Method of making a golf ball with a multi-layer core

ABSTRACT

A method for making a multilayer golf ball including a solid center having a center hardness, a plurality of laminates cut into a plurality of shapes formed around the center to create an inner ball, and a cover formed around the inner ball, wherein the plurality of layers can include at least a first layer having a hardness greater than the center hardness and a second layer having a hardness greater than the first layer hardness, and optionally a third layer disposed between the first and the second layers having a hardness greater than the first layer hardness.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of the U.S. patentapplication Ser. No. 09/948,692, filed Sep. 10, 2001, which is acontinuation-in-part of U.S. patent application Ser. No. 09/172,608,filed Oct. 15, 1998, now U.S. Pat. No. 6,302,808, which is a divisionalof U.S. patent application Ser. No. 08/943,932, filed Oct. 3, 1997, nowU.S. Pat. No. 6,056,842, and also a continuation-in-part of U.S. patentapplication Ser. No. 09/630,387, filed Aug. 1, 2000, which is acontinuation-in-part of U.S. patent application Ser. No. 08/603,057,filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676, and acontinuation-in-part of U.S. patent application Ser. No. 08/996,718,filed Dec. 23, 1997, now U.S. Pat. No. 6,124,389, which is acontinuation-in-part of U.S. patent application Ser. No. 08/746,362,filed Nov. 8, 1996, now U.S. Pat. No. 5,810,678, which is acontinuation-in-part of U.S. patent application Ser. No. 08/706,008,filed Aug. 30, 1996, now U.S. Pat. No. 5,813,923, which is acontinuation-in-part of U.S. patent application Ser. No. 08/603,057,filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676, which is acontinuation-in-part of U.S. patent application Ser. No. 08/482,522,filed Jun. 7, 1995, now U.S. Pat. No. 5,688,191, the disclosures ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention is directed to a method for making amultilayer golf ball having a plurality of laminates formed around theball. The plurality of laminates may be formed into shells by athermoforming process. The shells are then joined to form laminatelayers around the golf ball.

[0003] The plurality of laminate layers may have varying properties thatmay be arranged to produce a desired ball performance. The plurality oflaminate layers may include, for instance, at least a first laminatelayer having a hardness greater than the hardness of the golf ballcenter and a second laminate layer having a hardness greater than thefirst laminate layer hardness. An additional laminate layer also may bedisposed between the first and second intermediate layers having ahardness greater than the first laminate layer. The laminate layers maybe thermoplastic or thermoset materials.

BACKGROUND OF THE INVENTION

[0004] Golf ball manufacturers constantly strive to construct golf ballswith a balance of good “feel,” distance, and durability. Adjusting theconstruction of the ball (e.g., providing multiple layers of materialhaving differing material properties) and/or the composition of theindividual layers (e.g., using materials having a desired high flexuralmodulus, COR, or hardness) allows golf ball manufacturers to tweak ballproperties to obtain the desired balance of golf ball properties.

[0005] Golf balls today can be of varied construction, e.g., two pieceballs, three piece balls, the latter including wound balls. Thedifference in play characteristics resulting from these different typesof constructions can be quite significant.

[0006] Generally, golf balls have been classified as solid or woundballs. Solid balls having a two piece construction, typically acrosslinked rubber core, e.g., polybutadiene crosslinked with zincdiacrylate and/or similar crosslinking agents, encased by a blendedcover, e.g., ionomer resins, are generally most popular with the averagerecreational golfer. The combination of the core and cover materialsprovide a “hard” ball that is virtually indestructible by golfers andone that imparts a high initial velocity to the ball, resulting inimproved distance. Because the materials of which the ball is formed arevery rigid, two piece balls have a hard “feel” when struck with a club.Likewise, due to their hardness, these balls have a relatively low spinrate which provides greater distance.

[0007] Wound balls are generally constructed from a liquid or solidcenter surrounded by tensioned elastomeric material and covered with adurable cover material, e.g., ionomer resin, or a softer cover material,e.g., balata or polyurethane. Wound balls are generally thought of asperformance golf balls and have good resiliency, desirable spincharacteristics, and feel when struck by a golf club. However, woundballs are generally difficult to manufacture when compared to solid golfballs.

[0008] The prior art includes a variety of golf balls that have beendesigned to provide particular playing characteristics. Thesecharacteristics are generally the initial velocity and spin of the golfball, which can be optimized for various types of players. For instance,certain players prefer a ball that has a high spin rate in order tocontrol and stop the golf ball. Other players prefer a ball that has alow spin rate and high resiliency to maximize distance. Generally, agolf ball having a hard core and a soft cover will have a high spinrate. Conversely, a golf ball having a hard cover and a soft core willhave a low spin rate. Golf balls having a hard core and a hard covergenerally have very high resiliency for distance, but are hard feelingand difficult to control around the greens. A number of patents, forexample, have been issued which are directed towards directed towardsimproving the carry distance of conventional two piece balls by alteringthe typical single layer core and single cover layer construction toprovide a multi-layer ball, e.g., a dual cover layer, dual core layer,and/or a ball having an intermediate layer disposed between the coverand the core. U.S. Pat. Nos. 4,863,167, 5,184,828, and 4,714,253 areexamples of such multilayer golf balls.

[0009] In addition, there are a number of patents directed to improvingthe spin, click and feel of solid balls while maintaining the distanceprovided by the solid construction golf balls. U.S. Pat. Nos. 5,072,944,4,625,964, 4,650,193, and 4,848,770 disclose a golf ball having a rubbercore and intermediate layer, e.g., polybutadiene, surrounded by a cover.U.S. Pat. Nos. 5,253,871, 5,681,898, 5,439,227, 5,556,098 are directedto golf balls having intermediate layers using a variety of materialsother than polybutadiene.

[0010] Further, there are also several patents directed to golf ballshaving multiple cover layers. U.S. Pat. Nos. 4,431,193, 5,314,187, and4,919,434 are examples of such patents. Additional examples of golfballs with multiple layers include U.S. Publication No. 2002/0028885 A1and U.S. Pat. Nos. 6,319,153 and 6,299,550.

[0011] Moreover, while the benefits of laminate layers may be generallyrecognized, manufacturing laminate layers on a golf ball presentsseveral challenges that have largely precluded their use. For example,as the desired thickness of the laminate layers becomes thinner, it isincreasingly more difficult to maintain a relatively uniform layerthickness and concentric orientation around the ball using conventionalmanufacturing methods known in the golf industry.

[0012] Retractable pin injection molding, for example, uses pins thatpress against the core to hold it in place in the mold while layermaterial is being injected around it. The forces applied to the core tohold it in place may cause the core surface to deform slightly. Theportion of the core near the pins may deform inwards, while otherportions of the core may deform outward. Thus, when being secured inplace by retractable pins, portions of the surface of the core areslightly closer to the mold walls than other portions. When the injectedmaterial is intended to form a thin layer, these slight differences canpresent significant percentage deviations in thickness. Compressionmolding, which physically compresses both the layer material and thecore in order to form the layer, presents similar manufacturingdifficulties as the desired layer thickness becomes thin.

[0013] Recent developments in casting layers of the golf ball haveallowed for the manufacture of thin multilayer covers. But the castingprocess usually requires additional manufacturing time in order to allowthe cast material to sufficiently harden or cure before opening themold. Moreover, the use of casting only allows for one layer to beformed on the golf ball at a time. Thus, the manufacture of a golf ballhaving a plurality of laminate layers would require even more time. Inaddition, casting also involves close control over the selection andcombination of a suitable curing agent with a pre-polymer.

[0014] Thus, it would be advantageous to provide a method ofmanufacturing golf balls with laminate layers without significantlyincreasing manufacturing costs or manufacturing time.

SUMMARY OF THE INVENTION

[0015] The present invention is directed to the use of thermoformingprocesses to make an improved golf ball having a plurality of laminatelayers. The invention includes a golf ball having a plurality oflaminate layers that form at least a portion of the golf ball. Thelaminate layers may form, for example, all or part of the core,intermediate layers, or cover layers of the ball.

[0016] One embodiment of the present invention is directed to a methodof making a golf ball by thermoforming a plurality of shells,positioning them around a core, and forming a cover. The plurality ofshells may be formed from laminated roll stock material. In oneembodiment, the roll stock may have first and second lamination layersthat differ in hardness by about 10 shore D or more. In anotherembodiment, the difference in hardness between the first and secondlamination layers may be even greater, such as about 15 shore D or more,or even about 20 shore D or more.

[0017] In yet another embodiment, the step of thermoforming a pluralityof shells involves forming a sheet of shells from a roll stock. Theshells formed in the sheet of roll stock material may then be cut out ofthe sheet individually, in pairs or multiple pairs, in strips of shells,and the like. A lip or ring may be formed around the edge of the shellswhen they are cut out of the thermoformed sheet of roll stock. In oneembodiment, the lip extends in a radial direction from the edge of theshell from about 0.01 inches to about 0.25 inches. The lip or ring maybe any shape, but in one embodiment the shape is approximately circular.Once formed, the shells may then be joined around a core. In oneembodiment, the first and second shells have similar construction anddimensions. Once in position, the shells may be compression molded aboutthe core.

[0018] The lamination layers may be any desired thickness. In oneembodiment, each lamination layer has a thickness of about 0.1 inches orless. In another embodiment, each lamination layer has a thickness ofabout 0.05 inches or less. It is not required that the lamination layershave the same thickness. In one embodiment, the outermost laminationlayer is about 0.1 inches or less, while in another embodiment it isabout 0.05 inches or less.

[0019] The materials used for the thermoformed laminate layers need notbe the same as other layers. In one embodiment, at least one laminationlayer comprises a thermoset material. For example, the thermosetmaterial may be polybutadiene. In another embodiment, at least onelamination layer comprises a thermoplastic material. The thermoplasticmaterial may have a flexural modulus of about 10,000 psi or less.Additionally, the thermoplastic material may be made of ionomer resin,dynamically vulcanized thermoplastic elastomers, functionalizedstyrene-butadiene elastomers, thermoplastic rubbers, thermoplasticurethanes, metallocene polymers, ionomer resins, or blends thereof.Other materials having different characteristics, compositions, andproperties may be used as well.

[0020] The cover may be formed by injection molding, compressionmolding, casting, or thermoforming process, although any additionalmolding processes may be used as well. The cover may comprise one ormore layers of material. If desired, the outermost cover may have athickness of about 0.05 inches or less. Additionally, the golf ball mayhave a PGA compression of about 85 or less. In another embodiment, thegolf ball has a PGA compression of about 100 or less.

[0021] In one embodiment, the shell has at least a first and secondlamination layer, with the first lamination layer being closer to thecore than the second layer. In one embodiment, the hardness of the core,first layer, and second layer may be progressively harder from the coreto the second lamination layer. In another embodiment, the hardness ofthe core, first layer, and second layer becomes progressively softer. Inone embodiment, the differences between the hardness of the core andfirst lamination layer, and between the first and second laminationlayers is about 5 shore D or more. In another embodiment, the differenceis about 10 shore D or more.

[0022] Additional lamination layers may be thermoformed as well. Forinstance, one embodiment comprises a third laminate layer disposedbetween the first and second lamination layers. As mentioned above, thechanges in hardness from core to the second lamination layer may beprogressively harder or softer, although other combinations of hardnessmay be used as well.

[0023] The present invention is likewise directed to golf balls havingat least one thermoformed layer The thermoformed layer may form part orall of a cover, intermediate layer, core, or combination thereof. Asdescribed herein, the golf ball may have multiple laminate layers madeof a variety of materials.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a cross-sectional view of a golf ball formed accordingto the present invention;

[0025]FIG. 2 is a perspective view of a laminate including three layersof core material;

[0026]FIG. 3 is a sectional view of rollers and material being formedinto the laminate of core material;

[0027]FIG. 4 is a sectional view of a mold for forming multiple layersabout a core center according to the present invention;

[0028]FIG. 5 is a sectional view of a mold forming multiple layers abouta core center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold;

[0029]FIG. 6 is a sectional view of a mold forming multiple layers abouta core center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold;

[0030]FIG. 7 is a perspective view of a half mold for use in formingmultiple layers about core centers according to the present invention;

[0031]FIG. 8 is a cross-sectional view of a compression mold of a golfball core according to the present invention;

[0032]FIG. 9 is an exploded view of a golf ball core according to thepresent invention in a retractable-pin injection mold;

[0033]FIG. 10 is a cross-sectional view of a golf ball core according tothe present invention in a retractable-pin injection mold;

[0034]FIG. 11 is a cross-sectional view of a golf ball according to thepresent invention in a retractable-pin mold;

[0035]FIG. 12 is an exploded view of a golf ball core according to thepresent invention with cover layer hemispheres in a compression mold.

[0036]FIG. 13 is a perspective view of a molding apparatus forthermoforming laminate layers of a golf ball;

[0037] FIGS. 14A-F are illustrations of a thermoforming process for usein forming laminate golf ball layers;

[0038] FIGS. 15A-D are illustrations of a plug-assisted thermoformingprocess for use in forming laminate golf ball layers;

[0039]FIG. 16 is a perspective view of two thermoformed shells that jointo form a plurality of laminate layers around a golf ball;

[0040]FIG. 17 is a perspective view of a web assembly of thermoformedshells.

DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention is directed to golf balls having aplurality of laminate layers formed by thermoforming sheets of materialinto shells. The shells are then joined together to form the laminatelayers of the ball. The plurality of laminate layers may form anyportion of the golf ball, including the core, an intermediate layer, orthe cover.

[0042] One advantage of the present invention is that it allows for themanufacture of golf balls having thin layers of material of a relativelyuniform thickness. The present invention also allows laminate layers tobe more easily formed concentric with the center of the ball. The resultis greater flexibility in the design of golf balls in order to obtainexcellent playing characteristics, such as resiliency, spin rate, andfeel. Moreover, the present invention also simplifies the manufacturingprocess for making such laminate layers and thereby reducesmanufacturing costs.

[0043] In particular, the present invention uses raw material in rollstock form to form the shells of the ball by a thermoforming process.Thermoforming processes are high volume methods of producing moldedproducts from a thin sheet of roll stock. While this molding process isprincipally used with thermoplastic materials, it is also possible touse thermoset materials as well.

[0044] Thermoforming processes generally involve heating a sheet ofmaterial until the sheet softens and then forcing the sheet against acool forming mold by vacuum or pressure. Positive or negative pressureis then employed to push, pull, or stretch the softened sheet into acavity or onto a protrusion corresponding to the shape of the desiredpart. The sheet is held in place against the mold surface while itcools. Once it has sufficiently cooled, the sheet retains the shape ofthe mold even after being removed from the cavity or protrusion. Thereare several variations of thermoforming, such as vacuum, positive airpressure, plug assist, draping, twin sheet, positive, negative, vacuumsnap-back, and billow forming. Some of these techniques are explained ingreater detail below to illustrate the invention, although a skilledartisan would understand that a wide variety of additional thermoformingtechniques could be used without departing from the spirit and scope ofthe invention.

[0045] The sheet of material used in a thermoforming process may beprovided in roll stock. Generally, roll stock is a sheet of materialthat is rolled along its length to form a cylindrical shape. Typically,the roll stock is about 420 mm to about 660 mm wide, and has a thicknesscorresponding approximately to the desired thickness of the finishedproduct or layer. As explained more fully below, the roll stock isconnected to a thermoforming machine and delivered to the formingmodule.

[0046]FIG. 13 illustrates one embodiment of a thermoforming mold thatmay be used with the present invention. As shown, the thermoformingmachine or process can carry out several stages of the molding processsimultaneously. For instance, a portion of the roll stock may be beingpre-heated while other portions of the roll stock are being molded,undergoing further processing or finishing, or are being off-loaded forfurther processing at another location.

[0047] Roll stock is connected to the thermoforming machine at a loadingstation. In this embodiment, roll stock is rolled or wrapped around acylindrical tube that may be placed on a roller so that it can rotate aslayer material is supplied to the forming module. As the material isunwound, it is preheated and then molded into its desired shape.

[0048] In one embodiment of the present invention, the material isformed into a plurality of shells. The desired number of shells moldedin a single molding cycle may vary according to the size of the rollstock, although other factors also may determine what number of shellsare formed in each molding cycle as well. As the width of the roll stockincreases, the number of shells that may be formed in a single moldcycle increases. For instance, if the roll stock is about 660 mm wide,the number of shells that may be formed in a single molding cycle may beabout 65 shells or more, more preferably about 85 shells or more, andeven more preferably about 100 shells or more. In contrast, if a rollstock is about 420 mm wide, the number of shells that may be formed in asingle molding cycle may be about 40 or more, more preferably about 50or more, and even more preferably about 60 or more.

[0049] The duration of a mold cycle may be determined by the length oftime it takes from loading roll stock material into the mold to removingit from the mold. Preferably, a single mold cycle is relatively short induration. For example, a single mold cycle may last approximately 30seconds or less, but more preferably lasts less than about 10 seconds.More preferably, the cycle rate is approximately 10 cycles per minute.In this preferred embodiment, a thermoforming mold having 100 cavitiesand running at 10 cycles per minute can make approximately 1000 coversper minute.

[0050] The thermoforming mold in one embodiment of the present inventionhas a roll stock supply mechanism that controls the rate at which thesheet of material is fed into the molding machine. One example of asuitable stock supply mechanism is a servo driven chain drive, althoughone skilled in the art would understand that any method or structure maybe used to help move the roll stock through the molding process. In use,the supply mechanism delivers the sheet of roll stock to a pre-heatingstation—where the material is heated until soft. Once the material hasbeen sufficiently softened, the supply mechanism delivers the sheet ofroll stock to the mold cavities so that the material can be formed intothe desired shape. Once formed, the material is then delivered to anyadditional processing station or offloaded from the thermoformingmachine.

[0051] FIGS. 14A-F illustrate an example of a thermoforming process ingreater detail. In general the thermoforming process may be divided into6 steps. First, as shown in FIG. 14A, the roll stock is delivered to apreheating station where it is softened prior to being molded. In thisembodiment, the forming station is opened so that the roll stock may befed into the preheating station. Preferably, the roll stock is heldbetween the upper portion of the preheater and the heating elementsuntil the material is fully positioned within the preheater.

[0052] Next, with the reference to FIG. 14B, once the roll stock ispositioned within the preheater, the preheater is closed so that thelower surface of the roll stock is drawn near to or against the heatingplate. While the figures illustrate the lower portion or the mold movingupwards or downwards in order to close or open the mold, thisillustration does not limit the manner in which the portions of the moldmove with respect to each other. In one embodiment, a vacuum can beapplied to further assist in drawing the roll stock to the heatingplate. The heating elements of the thermoforming mold may use anysuitable structure or method to soften the roll stock. Examples of suchsuitable structures or methods may include, without limitation, radiantheat or ultrasonic vibration. Yet another example of a suitablestructure or method to soften the roll stock would include steam heatingor by electrically heating the roll stock. Two examples of infraredheaters that may be used to soften the roll stock are ceramic heatersand quartz tube heaters.

[0053] It is preferred that the roll stock be sufficiently softened sothat they can deform easily. Over time, such as by repeated moldingcycles, the mold plates can rise in temperature due to the dissipationof heat from the molded material. If the mold plates become too hot,however, the material may not cool sufficiently to allow it to set inits desired shape. To address the build-up of heat, the walls of themold cavity may be chilled so that as the material is quenced or cooledas it comes into contact with the cavity wall. The cooling of the moldmay be accomplished by any suitable means known to those skilled in theart. For instance, the mold may be chilled with water or glyol. Aircooling the mold cavity may also help maintain the mold below thedistortion or set temperature of the sheet of material.

[0054] Turning now to FIG. 14C, once the roll stock has been adequatelysoftened, the preheater may be aerated to equalize the pressure betweenthe inside of the preheater and the outside. This step is particularlyhelpful when a vacuum is used to draw the roll stock to the heatingplate as described above. Once the pressure has become relativelyequalized, the mold is opened so that the roll stock may be transportedto and positioned over the mold cavities as shown in FIG. 14D. As shownin FIG. 14D, the delivery of the softened roll stock to the moldcavities in turn may cause additional material to be supplied to thepreheater. In this embodiment, it is preferably that the time needed forsoftening the material and the time needed to form and cool the sheetagainst the mold surface are controlled so that both processes arecompleted at about the same time.

[0055] Once the softened roll stock is properly positioned over thecavities, the mold is closed and a vacuum is applied to one side of themold to draw the softened material toward or against the mold wall. Thisstep is shown in FIG. 14E. Additionally, compressed air may be forcedinto the mold on the opposite side of the material where the vacuum isapplied in order to further ensure that the material is pressed againstthe mold wall. The material is then cooled as it is pressed against themold wall. Eventually, the material is sufficiently cooled that is willretain its molded shape.

[0056] Once cooled, the pressure in the mold is again equalized so thatthe mold can be opened and the molded material removed (FIG. 14F). Toaccomplish this, air may be vented into the portion of the mold wherethe vacuum was applied. Air also may be vented or vacuumed out of theportion of the mold where compressed gases were forced inside. As themolded material is removed, any additional portion of the roll stockbeing preheated may then be delivered to the mold.

[0057] One skilled in the art would appreciate that several variationsof the molding process described above are possible without departingfrom the spirit and scope of the present invention. FIGS. 15A-D, forexample, provides one alternative molding process that also falls withinthe scope of the present invention. These figures illustrate that a plugor other suitable device may be used to assist in drawing the softenedroll stock against the mold. For instance, FIG. 15A illustrates thatonce the roll stock is sufficiently soft, it is positioned within themold so that the plug resides above the material. As illustrated in FIG.15B, the use of a plug or similar structure preferably is combined withthe vacuum forming process described above. The mold is then closed, avacuum is applied and the plug is lowered to press the material againstthe mold wall. Compressed gasses also may be delivered into the upperportion of the mold, as shown in FIG. 15C.

[0058] Application of the vacuum, plug, and compressed air may be stagedso that the rate or degree that material is drawn to or held against themold can vary during the mold cycle. For example, the time at which theplug and compressed air are applied can be staged or delayed until thevacuum has first drawn the material toward the mold wall. The plug and,optionally, compressed air may then be applied to press the roll stockagainst the mold wall. Likewise, application of the plug and/orcompressed air against the roll stock may discontinue prior tocompletion of the mold cycle. Alternatively, the plug may be used toprestretch the sheet prior to applying a vacuum or compressed air. Oncethe molding cycle is nearly complete, the pressure in the mold isequalized so that the mold can be opened and the molded materialremoved.

[0059] In yet another alternative embodiment of the present invention, apositive forming process also may be used to thermoform a layer of agolf ball. For example, the softened sheet of material may be positionedover a male or positive mold. The sheet then may be draped over thepositive mold until the sheet forms a seal around the outer edge of themold. Trapped air may then be evacuated by vacuum holes along theprotrusion of the male mold. Alternatively, or in addition to applying avacuum, forced air or other gases may be applied to the opposite side ofthe sheet that contacts the mold, thereby blowing the sheet intoposition. The vacuum and/or applied pressure causes the sheet to bepressed against the mold surface while it cools.

[0060] Twin sheet thermoforming processes also may be used to form agolf ball layer. This process is similar to the vacuum process describedabove, but forms two sheets into opposing mold halves at the same time.The molded sheets may then be fused or connected together while thesheets are still in a softened state. Preferably, however, a golf ballcore is placed inside the formed sheets prior to them being connectedtogether.

[0061] In all of these examples, the formed material is removed from themold once the sheet has sufficiently cooled to retain the molded shape.Removal of the molded sheet may be assisted by applying pressurizedgases between the mold wall and the sheet of material. For instance,forced air may be directed through openings or vents on the mold surfacethat previously were used to form a vacuum. The use of pressurizedgasses to remove the formed sheet may be particularly beneficial inpositive forming, although it may be useful in other thermoformingprocesses as well.

[0062] As described above, the material may be molded into shells thatmay be joined to form the laminate layers of the golf ball. FIG. 16illustrates one example of an assembly of two shells applied over acomponent part of a golf ball, such as a core. The shells are generallyhemispherical in shape with inner diameters corresponding approximatelyto the outer diameter of the ball placed inside. In this embodiment, theshells used in the assembly have a molded lip that extends outward fromthe perimeter of the base of the shell.

[0063] Preferably, a plurality of shells are thermoformed during eachmolding cycle. Once molded, the sheet of molded shells can be preparedfor further processing. In the embodiment shown in FIG. 16, individualshells are cut from the molded sheet such that the shells have lips orrings. Preferably, the end of the shell corresponding approximately tothe equator of the ball has a ring or lip that extends outward inapproximately a radial direction so that when two shells are joinedaround a core or other golf ball component the surfaces of the moldedlips are approximately parallel.

[0064] Alternatively, as the molded roll stock is removed from the moldcavity, the shells may remain in the sheet as it is removed from themachine. Two sheets of molded roll stock may then be used to mold theshells around a plurality of centers placed within the shells. Inanother embodiment, the shells formed in the molded roll stock may bepunched out, cut, or otherwise separated from each other. For instance,the shells may be punched out from the sheet of molded roll stock andthen assembled around cores individually.

[0065] In yet another alternative embodiment, the shells may be cut fromthe roll stock in pairs, or multiple pairs, so that the cores may beplaced in a shell or plurality of shells on one side of the cut sheet.The sheet may then be folded so that a second shell is placed over thecore. The surfaces of the sheet that contact each other once the sheetis folded may be tack welded or otherwise joined so that the assembly ofcores and shells remains in a desired position for further processing.Alternatively, a crease may be formed where the sheet is folded to helpmaintain the positioning of the shells and cores. The crease may beformed by applying pressure, heat, or both along the folded edge of thesheet.

[0066] It is not necessary in every instance that the shells cut fromthe roll stock should be in pairs or multiple pairs. For example, thesheet may be cut so that a plurality of shells remain attached orconnected to each other. The sheet may be cut in strips, for instance,that correspond to the cavity configuration of at least a portion of acompression mold. Cores may be placed within the strip of shells. Oncethe cores are in position, a second set of shells may then be placedover them. The second set of shells may be a similarly configured stripcut from a larger sheet of thermoformed shells, may be individualshells, or may have a different configuration.

[0067] Returning to the embodiment shown in FIG. 16, the width of thelip from the outer surface of the shell to the outermost edge of thering may be any length, such as between about 0.05 inches to about 0.5inches or between about 0.063 inches and 0.3 inches. Depending upon thesubsequent processing steps that will be taken to complete themanufacture of the golf ball, the width of the lip may have a beneficialminimum length or maximum length. For instance, the minimum width of thelip may be at least about 0.63 inches, at least about 0.093 inches, atleast about 0.125 inches, or at least about 2 inches. Likewise, themaximum width of the lip may be about 0.3 inches or less, about 0.188inches or less, or about 0.125 inches or less. These upper and lowerlimits also may be combined in any manner. For example, the width of thelip may be between about 0.063 inches and about 0.188 inches, or may bebetween about 0.093 inches or about 0.125 inches.

[0068] When two shells are joined, the surfaces of the rings or lips maybe tacked together to hold the assembly together until it is ready foradditional processing. Additionally, the rings may assist in properlypositioning or aligning the shells in a mold in subsequent moldingprocesses for the ball, such as compression molding or other processesdescribed herein.

[0069] Yet another benefit of using molded lips or rings is that theinner surface of the shells may be molded to closely correspond to theouter surface of the component placed inside the shells. For instance, acore can be placed inside shells with inner surfaces having a curvatureclosely corresponding to the core's outer diameter. One benefit of thisconfiguration is that it may reduce or eliminate the occurrence oftrapped air or gases between the shells and the core during subsequentmolding. For example, the molded lips may be tacked together to hold theassembly together prior to compression molding the shells around thecore. Alternatively, the shells may be configured and adapted such thatfrictional forces hold the shell on the core.

[0070] The shells and ball may be placed in a compression mold to fusethe two shells together around the ball. Preferably the compression moldprimarily applies pressure and heat where the two shells meet, and doesnot apply uneven pressure to other portions of the ball.

[0071]FIG. 17 illustrates another embodiment of the invention in which asheet of molded shells are prepared for further processing without firstcutting individual shells as described above and illustrated in FIG. 16.Instead, the shells remain in the thermoformed sheet. Cores are thenplaced inside the shells and a second sheet of thermoformed material maythen be placed over the cores. The assembly of the sheets and cores maybe tack welded or held together in any suitable manner, examples ofwhich are already described herein.

[0072] The roll stock may be made of any material or combination ofmaterials according to the number and features of the laminate layersdesired to be formed on the golf ball. Many examples of the types ofmaterials that may be used are provided in greater detail below.Preferably, the roll stock is preformed with a plurality of layers, eachlayer corresponding to a laminate layer of the ball. Thus, the rollstock may be made of co-extruded films of material. The materialproperties of each film need not be identical, or even similar, to theneighboring laminate layer. For instance, one laminate layer may bethermoplastic, while another is thermoset. Additionally, the hardness ofone layer may be greater than the hardness of another. For instance, thehardness of one layer may have a hardness that is about 10 shore D orgreater than a neighboring layer. Additionally, in one embodiment thedifference in hardness between the laminate layers may be from about 3to about 20 shore D, but more preferably may be from about 5 to about 15shore D.

[0073] In another embodiment, the laminate layers may differ in hardnessby a lesser degree. For example, the layers may differ in hardness byfrom about 5 to 40 shore C, but also may differ in hardness by about 20shore C or less. More preferably, the laminate layers may differ inhardness by about 10 shore C.

[0074] The thermoformed laminate layer may be used to form any portionof the golf ball in whole or in part, including the core, anintermediate layer, or a cover. The following examples of variousembodiments of the invention further illustrate the types of golf ballsand laminate layers that may be made under the present invention. Askilled artisan would appreciate, however, that the following discussionillustrates the invention without limiting it to only the embodimentsdiscussed.

[0075]FIG. 1 shows a multilayer golf ball according to one embodiment ofthe present invention. Golf ball 10 includes a center 11, a first layer12, a second layer 13, a third layer 14, and a cover 15. The first,second, and third layers may be of the same or different material. Asused herein, the term “core layer” means any layer surrounding thecenter of the ball, but not the outermost layer, and, therefore, theterm may be used interchangeably with the term “intermediate layer.”

[0076] As used herein, the term “layer” includes any generally sphericalportion of a golf ball or golf ball core, center, intermediate, orcover, including a one-piece ball. An “intermediate layer” is definedherein as a portion of the golf ball that occupies a volume between thecover and the core. Of course, as one of ordinary skill in the art wouldrecognize, any of the core, cover, and intermediate of the golf balls ofthe invention can be formed of one layer or a plurality of layers, asthat term is defined herein.

[0077] As used herein, the term “multilayer” means at least two layersand includes fluid-center balls, hollow-center balls, and balls with atleast two intermediate layers and/or cover layers.

[0078] The following terms that are used in this application are definedin terms of the enumerated ASTM tests: Specific gravity ASTM D - 297Flexural (Flex) Modulus ASTM D - 6272-98, Procedure B Shore C & DHardness ASTM D - 2240-00 Melt flow index ASTM Test D 1238, Condition E,Procedure A

[0079] The Center

[0080] The golf balls of the present invention are formed with a centerhaving a low compression, but still exhibit a finished ball COR andinitial velocity approaching that of conventional two-piece distanceballs. Preferably, the center employed in the golf balls of the presentinvention have a compression of about 60 or less, more preferably about45 to about 60 and most preferably about 50 to about 55. As used herein,the term “about,” used in connection with one or more numbers ornumerical ranges, should be understood to refer to all such numbers,including all numbers in a range. Likewise, it is preferred that thefinished balls made with such centers have a COR, measured at an inboundspeed of 125 ft./s., of about 0.795 to about 0.815, more preferablyabout 0.797 to about 0.812 and most preferably about 0.800 to about0.810.

[0081] As used herein, “COR” refers to Coefficient of Restitution, whichis obtained by dividing a ball's rebound velocity by its initial (i.e.,incoming) velocity. This test is performed by firing the samples out ofan air cannon at a vertical steel plate over a range of test velocities(from 75 to 150 ft/s). A golf ball having a high COR dissipates asmaller fraction of its total energy when colliding with the plate andrebounding therefrom than does a ball with a lower COR. Unless otherwisenoted, the COR values reported herein are the values determined at anincoming velocity of 125 ft/s.

[0082] In a preferred embodiment, the center has a Shore C hardness ofabout 65 to about 80, more preferably about 68 to about 75 and mostpreferably about 72 to about 75.

[0083] The centers employed in the golf balls of the present inventionpreferably have a diameter of about 1.25 inches to about 1.51 inches,more preferably about 1.30 inches to about 1.48 inches and mostpreferably about 1.39 inches. The overall diameter of the center and theintermediate layer is about 84 percent to about 97 percent of theoverall diameter of the finished ball.

[0084] A representative base composition for forming the centersemployed in the present invention includes polybutadiene and, in partsby weight based on 100 parts polybutadiene, 20 to 50 parts of a metalsalt diacrylate, dimethacrylate, or monomethacrylate, preferably zincdiacrylate. The polybutadiene preferably has a cis-1,4 content of aboveabout 90 percent and more preferably above about 96 percent. Commercialsources of polybutadiene include Shell 1220 manufactured by ShellChemical, NEOCIS® BR40 manufactured by Enichem Elastomers, UBEPOL® BR150manufactured by Ube Industries, Ltd, and CB23 available BayerCorporation of Akron, Ohio. If desired, the polybutadiene can also bemixed with other elastomers known in the art, such as natural rubber,styrene butadiene, and/or isoprene in order to further modify theproperties of the center. When a mixture of elastomers is used, theamounts of other constituents in the center composition are usuallybased on 100 parts by weight of the total elastomer mixture.

[0085] Metal salt diacrylates, dimethacrylates, and monomethacrylatessuitable for use in the center employed in this invention include thosewherein the metal is magnesium, calcium, zinc, aluminum, sodium, lithiumor nickel. Zinc diacrylate is preferred, because it provides golf ballswith a high initial velocity in the United States Golf Association(“USGA”) test. The zinc diacrylate can be of various grades of purity.For the purposes of this invention, the lower the quantity of zincstearate present in the zinc diacrylate the higher the zinc diacrylatepurity. Zinc diacrylate containing less than about 10 percent zincstearate is preferable. More preferable is zinc diacrylate containingabout 4 to about 8 percent zinc stearate. Suitable, commerciallyavailable zinc diacrylates include those from Rockland React-Rite andSartomer. The preferred concentrations of zinc diacrylate that can beused are 20 to 50 parts per hundred (pph) based upon 100 pph ofpolybutadiene or alternately, polybutadiene with a mixture of otherelastomers that equal 100 pph. As used herein, the term “pph” inconnection with a batch formulation refers parts by weight of theconstituent per hundred parts of the base composition.

[0086] Free radical initiators are used to promote cross-linking of themetal salt diacrylate, dimethacrylate, or monomethacrylate and thepolybutadiene. Suitable free radical initiators for use in the inventioninclude, but are not limited to peroxide compounds, such as dicumylperoxide; 1,1-di(t-butylperoxy) 3,3,5-trimethyl cyclobexane;bis(t-butylperoxy) diisopropylbenzene; 2,5-dimethyl-2,5di(t-butylperoxy) hexane; or di-t-butyl peroxide; and mixtures thereof.Other useful initiators would be readily apparent to one of ordinaryskill in the art without any need for experimentation. The initiator(s)at 100 percent activity are preferably added in an amount rangingbetween about 0.05 and about 2.5 pph based upon 100 parts of butadiene,or butadiene mixed with one or more other elastomers. More preferably,the amount of initiator added ranges between about 0.15 and about 2 pphand most preferably between about 0.25 and about 1.5 pph.

[0087] Typical prior art golf ball centers incorporate 5 to 50 pph ofzinc oxide (ZnO) in a zinc diacrylate-peroxide cure system thatcross-links polybutadiene during the core molding process. However, inone embodiment of the present invention the ZnO in the centercomposition may be eliminated in favor of calcium oxide (CaO). Centersproduced from an admixture containing CaO may exhibit desirableperformance properties. For instance, when replacing ZnO with CaO mayallow the initial velocity and COR of the center to be maintained whilereducing the compression of the center by at least about 4 compressionpoints on the standard compression scale, and may be reduced as much as6 points.

[0088] As used herein, the terms “points” or “compression points” referto the compression scale or the compression scale based on the ATTIEngineering Compression Tester. This scale, which is well known to thoseworking in this field, is used in determining the relative compressionof a center or ball. Some artisans use the Reihle compression scaleinstead of the standard compression scale. Based on disclosure in U.S.Pat. No. 5,368,304, column 20, lines 55-53 it appears that Reihlecompression values can be converted to compression values through theuse of the following equation:

compression value=160−Reihle compression value.

[0089] Additionally, the combination of the use of calcium oxide and ahigher percentage of zinc diacrylate can be used to maintain the samecompression as with the zinc oxide, but the initial velocity and COR issignificantly increased. Thus, by using calcium oxide, either the centercompression can be lowered and the initial velocity and COR maintainedor the amount of zinc diacrylate can be increased so that the centercompression is the same and the initial velocity and COR is increased.

[0090] The amount of calcium oxide added to the center-formingcomposition may be from about 0.1 to about 15, preferably 1 to 10, mostpreferably 1.25 to 5, parts calcium oxide per hundred parts ofpolybutadiene.

[0091] In yet another, more preferred, embodiment, however, the core mayinclude halogenated organosulfur compounds, such as those described inapplication Ser. No. 09/951,963 filed on Sep. 13, 2001, the entirety ofwhich is incorporated herein by reference. The halogenated organosulfercompunds of the present invention may include, but are not limited tothose having the general formula:

[0092] where R₁-R₅ can be C₁-C₈ alkyl groups; halogen groups; thiolgroups (—SH), carboxylated groups; sulfonated groups; and hydrogen; inany order; and also pentafluorothiophenol; 2-fluorothiophenol;3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol;2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their zinc salts, the metal saltsthereof, and mixtures thereof, but is preferably pentachlorothiophenolor the metal salt thereof. The metal salt may be zinc, calcium,potassium, magnesium, sodium, and lithium, but is preferably zinc.

[0093] Preferably, the halogenated organosulfur compound ispentachlorothiophenol, which is commercially available in neat form orunder the tradename STRUKTOL®, a clay-based carrier containing thesulfur compound pentachlorothiophenol loaded at 45 percent (correlatingto 2.4 parts PCTP). STRUKTOL® is commercially available from StruktolCompany of America of Stow, OH. PCTP is commercially available in neatform from eChinachem of San Francisco, Calif. and in the salt form fromeChinachem of San Francisco, Calif. Most preferably, the halogenatedorganosulfur compound is the zinc salt of pentachlorothiophenol, whichis commercially available from eChinachem of San Francisco, Calif. Thehalogenated organosulfur compounds of the present invention arepreferably present in an amount greater than about 2.2 pph, morepreferably between about 2.3 pph and about 5 pph, and most preferablybetween about 2.3 and about 4 pph.

[0094] The center compositions employed in the present invention mayalso include fillers, added to the elastomeric composition to adjust thedensity and/or specific gravity of the center. As used herein, the term“fillers” includes any compound or composition that can be used to varythe density and other properties of the subject golf ball center.Fillers useful in the golf ball center according to the presentinvention include, for example mineral fillers such as zinc oxide (in anamount significantly less than that which would be necessary without theaddition of the calcium oxide), barium sulfate, and regrind (which isrecycled core molding matrix ground to 30 mesh particle size). Otherexamples of fillers include, but are not limited to tungsten and clays.The amount and type of filler utilized is governed by the amount andweight of other ingredients in the composition, since a maximum golfball weight of 1.620 oz has been established by the USGA. Appropriatefillers generally used range in specific gravity from about 2.0 to about5.6, although the specific gravity of some fillers may be even higher.The specific gravity of a tungsten filler, for instance, may be about19. In the preferred golf ball, the amount of filler in the center islower than that of a typical golf ball such that the specific gravity ofthe center is decreased.

[0095] The preferred range of specific gravities of the centers employedin the present invention is from about 1.0 to about 1.2, more preferablyin the range of about 1.1 to about 1.18, depending upon the size of thecenter, cover, intermediate layer and finished ball, as well as thespecific gravity of the cover and intermediate layer.

[0096] Other ingredients such as accelerators, e.g. tetra methylthiuram,processing aids, processing oils, plasticizers, dyes and pigments,antioxidants, as well as other additives well known to the skilledartisan may also be used in the present invention in amounts sufficientto achieve the purpose for which they are typically used.

[0097] The Intermediate Layer(s)

[0098] The intermediate layer(s) may be formed from dynamicallyvulcanized thermoplastic elastomers, functionalized styrene-butadieneelastomers, thermoplastic rubbers, thermoset elastomers, thermoplasticurethanes, metallocene polymers, thermoset urethanes, ionomer resins, orblends thereof. In a preferred embodiment of the present invention, theintermediate layer includes a thermoplastic or thermoset polyurethane.

[0099] Suitable dynamically vulcanized thermoplastic elastomers includeSANTOPRENE®, SARLINK®, VYRAM®, DYTRON® and VISTAFLEX®. SANTOPRENE® isthe trademark for a dynamically vulcanized PP/EPDM. SANTOPRENE® 203-40is an example of a preferred SANTOPRENE® and is commercially availablefrom Advanced Elastomer Systems.

[0100] Examples of suitable functionalized styrene-butadiene elastomers,i.e., styrene-butadiene elastomers with functional groups such as maleicanhydride or sulfonic acid, include KRATON FG-1901x and FG-1921x, whichare available from the Shell Corporation of Houston, Tex.

[0101] Examples of suitable thermoplastic polyurethanes include ESTANE®58133, ESTANE® 58134 and ESTANE® 58144, which are commercially availablefrom the B. F. Goodrich Company of Cleveland, Ohio.

[0102] Suitable metallocene polymers, i.e., polymers formed with ametallocene catalyst include those commercially available from SentinelProducts of Hyannis, Mass. Suitable thermoplastic polyesters includepolybutylene terephthalate.

[0103] Suitable thermoplastic ionomer resins are obtained by providing across metallic bond to polymers of monoolefin with at least one memberselected from the group consisting of unsaturated mono- or di-carboxylicacids having 3 to 12 carbon atoms and esters thereof (the polymercontains 1 to 50 percent by weight of the unsaturated mono- ordi-carboxylic acid and/or ester thereof). More particularly, low modulusionomers such as acid-containing ethylene copolymer ionomers, includeE/X/Y copolymers where E is ethylene, X is a softening comonomer such asacrylate or methacrylate present in 0-50 (preferably 0-25, mostpreferably 0-2), weight percent of the polymer, and Y is acrylic ormethacrylic acid present in 5-35 (preferably 10-35, most preferably15-35, making the ionomer a high acid ionomer) weight percent of thepolymer, wherein the acid moiety is neutralized 1-90 percent (preferablyat least 40 percent, most preferably at least about 60 percent) to forman ionomer by a cation such as lithium*, sodium*, potassium, magnesium*,calcium, barium, lead, tin, zinc* or aluminum (*=preferred), or acombination of such cations. Specific acid-containing ethylenecopolymers include ethylene/acrylic acid, ethylene/methacrylic acid,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include ethylene/methacrylic acid, ethylene/acrylicacid, ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

[0104] Such ionomer resins include SURLYN® and Iotek®, which arecommercially available from DuPont and Exxon, respectively.

[0105] In another preferred embodiment of the present invention, theintermediate layer is a blend of a first and a second component whereinthe first component is a dynamically vulcanized thermoplastic elastomer,a functionalized styrene-butadiene elastomer, a thermoplastic orthermoset polyurethane or a metallocene polymer and the second componentis a material such as a thermoplastic or thermoset polyurethane, athermoplastic polyetherester or polyetheramide, a thermoplastic ionomerresin, a thermoplastic polyester, another dynamically vulcanizedelastomer, another a functionalized styrene-butadiene elastomer, anothera metallocene polymer or blends thereof In a more preferred embodiment,at least one of the first and second components includes a thermoplasticor thermoset polyurethane.

[0106] Such thermoplastic blends useful in the intermediate layers ofthe golf ball of the present invention preferably include about 1percent to about 99 percent by weight of a first thermoplastic and about99 percent to about 1 percent by weight of a second thermoplastic.Preferably the thermoplastic blend includes about 5 percent to about 95percent by weight of a first thermoplastic and about 5 percent to about95 percent by weight of a second thermoplastic. In a preferredembodiment of the present invention, the first thermoplastic material ofthe blend is a dynamically vulcanized thermoplastic elastomer, such asSantoprene®.

[0107] The intermediate layer of the present invention may be formedfrom an intermediate layer blend including up to 100 percent by weightof an ethylene methacrylic/acrylic acid copolymer. As used herein, theterm “copolymer” refers to a polymer which is formed from two or moremonomers. Below is a non-limiting example of the chemical structure forsuitable ethylene methacrylic/acrylic acid copolymers:

[0108] wherein

[0109] x=50 to 99 percent;

[0110] y=1 to 50 percent;

[0111] z=0 to 49 percent;

[0112] R₁=H or CH₃;

[0113] R₂=CH₃ or isobornyl; and

[0114] n=0 to 12.

[0115] Specific acid-containing ethylene copolymers includeethylene/acrylic acid; ethylene/methacrylic acid; ethylene/acrylicacid/n- or isobutyl acrylate; ethylene/methacrylic acid/n- or iso-butylacrylate; ethylene/acrylic acid/methyl acrylate; ethylene/methacrylicacid/methyl acrylate; ethylene/acrylic acid/iso-bornyl acrylate ormethacrylate and ethylene/methacrylic acid/isobornyl acrylate ormethacrylate. Suitable ethylene methacrylic/acrylic acid copolymers aresold commercially by DuPont under the tradename NUCREL®, with NUCREL®960, NUCREL® RX9-1, and 010 being preferred.

[0116] In one embodiment, the intermediate layer is formed from a blendwhich includes an ethylene methacrylic/acrylic acid copolymer.

[0117] In another embodiment of the present invention, the intermediatelayer is formed from a blend which includes an ethylenemethacrylic/acrylic acid copolymer and a second component which includesa thermoplastic material. Suitable thermoplastic materials for use inthe intermediate blend include, but are not limited to, polyesteresterblock copolymers, polyetherester block copolymers, polyetheramide blockcopolymers, ionomer resins, dynamically vulcanized thermoplasticelastomers, styrene-butadiene elastomers with functional groups such asmaleic anhydride or sulfonic acid attached, thermoplastic polyurethanes,thermoplastic polyesters, polymers formed using a metallocene catalyst(“metallocene polymers”) and/or blends thereof.

[0118] Suitable thermoplastic polyetheresters include materials whichare commercially available from DuPont under the tradename HYTREL® andinclude HYTREL® 3078, HYTREL® G3548W, HYTREL® G4078W, and HYTREL® 4069.

[0119] Suitable thermoplastic polyetheramides are commercially availablefrom Elf-Atochem of Philadelphia, Pa., under the tradename PEBAX® andinclude PEBAX® 2533, PEBAX® 1205 and PEBAX® 4033.

[0120] Preferably, the second component of the intermediate layer blendincludes polyetherester block copolymer, with HYTREL® 3078 being aparticularly preferred polyetherester block copolymer.

[0121] Other conventional materials, such as balata, elastomer andpolyethylene may also be used in the first, second and third layers 12,13 and 14 of the present invention.

[0122] Many prior art intermediate layers generally have a specificgravity of about 1 or less. However, in a preferred embodiment, theintermediate layer employed in the golf balls of the present inventionhave a specific gravity greater than 1.2, preferably about 1.21 to about1.30, more preferably about 1.23 to about 1.29 and most preferably about1.27.

[0123] The desired specific gravity of the intermediate layer may beobtained by adding a filler such as barium sulfate, zinc oxide, titaniumdioxide and combinations thereof to the intermediate layer blend. Zincoxide is the preferred filler.

[0124] In one embodiment of the present invention, the intermediatelayer is formed from a blend of about 1 to about 99 percent by weightethylene methacrylic/acrylic acid copolymer, about 0 to about 75 percentby weight of the second thermoplastic component (as described above) andabout 0 to about 50 percent by weight zinc oxide. In another embodimentof the present invention, the intermediate layer is formed from a blendof about 10 to 50 percent by weight ethylene methacrylic/acrylic acidcopolymer, 25 to 75 percent by weight of a second thermoplasticcomponent and about 5 to about 40 percent by weight zinc oxide. In amost preferred embodiment of the present invention, the intermediatelayer is formed from a blend of about 15 to about 25 percent by weightethylene methacrylic/acrylic acid copolymer, about 50 to about 60percent by weight of a second thermoplastic component and about 20 toabout 30 percent by weight zinc oxide. In another embodiment of theinvention, the second thermoplastic component is present in theintermediate layer blend in an amount of less than 50 percent by weight,and preferably 30 to 45 percent by weight. A specific example of thisembodiment is an intermediate layer composition including about 57percent by weight HYTREL® 3078, about 20 percent by weight NUCREL® 960,and about 23 percent by weight zinc oxide.

[0125] The intermediate layer blend preferably has a flexural modulus ofless than about 10,000 psi, more preferably about 5,000 to about 8,000psi and most preferably about 7,500 psi. Likewise, the intermediatelayers employed in the golf balls of the present invention preferablyhave a Shore D hardness of about 35 to 50, more preferably about 37 toabout 45 and most preferably about 40.

[0126] Preferably, the intermediate layer and core construction employedin the present invention have a compression of less than about 65, morepreferably about 50 to about 65, and most preferably about 50 to 55.

[0127] The intermediate layer employed in the golf balls of the presentinvention preferably have a thickness from about 0.020 inches to about0.125 inches, more preferably about 0.035 inches to about 0.085 inchesand most preferably about 0.06 inches The outer diameter of theintermediate layer is preferably about 1.510 inches.

[0128] The golf balls of the present invention may include a pluralityof intermediate layers, e.g., a first intermediate layer adjacent thecore and a second intermediate layer adjacent the cover. The firstintermediate layer may include the materials as discussed above.Preferably, the first intermediate layer includes a thermoplasticmaterial and has a greater hardness than the core. The secondintermediate layer may be disposed around the first intermediate layerand preferably has a greater hardness than the first intermediate layer.

[0129] The second intermediate layer may be formed of materials such aspolyether or polyester thermoplastic urethanes, thermoset urethanes, andionomers such as acid-containing ethylene copolymer ionomers, includingE/X/Y terpolymers where E is ethylene, X is an acrylate ormethacrylate-based softening comonomer present in 0 to 50 weight percentand Y is acrylic or methacrylic acid present in 5 to 35 weight percent.More preferably, in a low spin rate embodiment designed for maximumdistance, the acrylic or methacrylic acid is present in 15 to 35 weightpercent, making the ionomer a high modulus ionomer.

[0130] In one embodiment, the second intermediate layer is formed ofcomposition including at least one high acid ionomer. As used herein,the term “high acid ionomer”, is an ionomer resin wherein Y is acrylicor methacrylic acid units present from about 17 weight percent to about35 weight percent in the polymer. Generally, a high acid ionomer willhave a Shore D hardness of about 60 or greater and a flexural modulus ofabout 50,000 psi or greater, preferably from about 50,000 psi to about125,000 psi. In the vernacular of the golf ball art, high acid ionomersare sometimes referred to as “hard” ionomers.

[0131] In another embodiment, the second intermediate layer ispreferably formed of a thermoset material, preferably having a flexuralmodulus of about 50,000 psi or greater. In one embodiment, the thermosetmaterial is polybutadiene.

[0132] In one embodiment, the second intermediate layer is adjacent thecover and has a hardness greater than that of the first intermediatelayer.

[0133] A third intermediate layer may be disposed in between the firstand second intermediate layers. The third intermediate layer may beformed of the variety of materials as discussed above. In oneembodiment, the third intermediate layer is disposed in between thefirst and second intermediate layers and preferably has a hardnessgreater than the hardness of the first intermediate layer.

[0134] The Cover Layer

[0135] The cover layer of the present invention may include at least onelayer of a thermoplastic or thermosetting material. Any number of a widevariety of cover materials may be used in the present invention such asionomer resins, polyurethanes, balata and blends thereof.

[0136] In one embodiment, the cover is formed of a composition includingvery low modulus ionomers (VLMIs). As used herein, the term “very lowmodulus ionomers”, or the acronym “VLMIs”, are those ionomer resinsfurther including a softening comonomer X, commonly a (meth)acrylateester, present from about 10 weight percent to about 50 weight percentin the polymer. VLMIs are copolymers of an α-olefin, such as ethylene, asoftening agent, such as n-butyl-acrylate or iso-butyl-acrylate, and anα,β-unsaturated carboxylic acid, such as acrylic or methacrylic acid,where at least part of the acid groups are neutralized by a magnesiumcation. Other examples of softening comonomers include n-butylmethacrylate, methyl acrylate, and methyl methacrylate. Generally, aVLMI will have a flexural modulus from about 2,000 psi to about 10,000psi. VLMIs are sometimes referred to as “soft” ionomers. U.S. Pat. No.6,144,415, which is incorporated in its entirety by reference herein,discloses suitable VLMIs for incorporation into the cover formulationsof the present invention. Ionomers, such as acid-containing ethylenecopolymer ionomers, include E/X/Y copolymers where E is ethylene, X is asoftening comonomer such as acrylate or methacrylate present in 0 to 50(preferably 0 to 25, most preferably 0 to 2), weight percent of thepolymer, and Y is acrylic or methacrylic acid present in 5 to 35(preferably 10 to 35, most preferably 15 to 20) weight percent of thepolymer, wherein the acid moiety is neutralized 1 to 90 percent(preferably at least 40 percent, most preferably at least about 60percent) to form an ionomer by a cation such as lithium, sodium,potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, or acombination of such cations, lithium, sodium and zinc being the mostpreferred. Specific acid-containing ethylene copolymers includeethylene/acrylic acid, ethylene/methacrylic acid, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl acrylate,ethylene/methacrylic acid/iso-butyl acrylate, ethylene/acrylicacid/iso-butyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate,ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methylacrylate, ethylene/methacrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylicacid/n-butyl methacrylate. Preferred acid-containing ethylene copolymersinclude ethylene/methacrylic acid, ethylene/acrylic acid,ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

[0137] As mentioned above, ionomer resins are commercially availablefrom E. I. DuPont de Nemours and Co. of Wilmington, Del., under thetradename SURLYN®, and from Exxon Corporation of Houston, Tex., underthe tradename IOTEK®. Some particularly suitable SURLYNS® includeSURLYN® 8140 (Na) and SURLYN® 8546 (Li) which have an methacrylic acidcontent of about 19 percent.

[0138] To aid in the processing of the cover stock, and as is well knownin the art, ionomer resins may be blended in order to obtain a coverhaving desired characteristics. For this reason, it is preferable thatthe covers of the golf balls of the present invention be formed from ablend of two or more ionomer resins. A particularly preferred covermaterial for use in the present invention is formed from a blend ofabout 50 percent by weight SURLYN® 7940, about 47 percent by weightSURLYN® 8940 and about 3 percent by weight SURLYN® 8660.

[0139] In one embodiment, the cover material includes a blend of a verysoft material and a harder material. Preferably, the cover includesabout 75 to about 25 parts by weight based on 100 parts by weight resin(pph) of a VLMI and about 25 pph to about 75 pph of a standard ionomerresin. Preferably, the VLMI is a sodium ionomer resin and constitutesabout 40 pph to about 60 pph of the ionomer blend and the standardionomer resin is a lithium ionomer resin and constitutes about 60 pph toabout 40 pph of the ionomer blend. Even more preferably, a 50/50 blendof the sodium and lithium ionomers with additives, e.g., colorconcentrate, is used for the cover composition. Suitable sodium ionomerresins include, but are not limited to SURLYN® 8320, SURLYN® 8269, andSURLYN® 8265.

[0140] The sodium ionomer resin is preferably a copolymer includingabout 95 to about 80 parts by weight of copolymer of ethylene and about5 to about 12 parts by weight of the copolymer of acrylic or methacrylicacid in which about 10 percent to about 90 percent of the acid groupsare neutralized by sodium. In one embodiment, the sodium ionomer resinused in the present invention has a flexural modulus between about 1,000and about 20,000 psi (5 and 140 MPa) and, more preferably, between about2,000 and about 10,000 psi (10 to 70 MPa).

[0141] The lithium ionomer resin is preferably a copolymer includingabout 95 to about 80 parts by weight of ethylene and about 10 to about16 parts by weight of acrylic or methacrylic acid based on 100 parts byweight copolymer. Preferably, the lithium ionomer resin has about 10percent to about 90 percent of the acid groups neutralized by lithium.Preferably, the lithium ionomer resin has a high flexural modulus whichis above about 60,000 psi (415 MPa). More preferably, the lithiumionomer resin used in the present invention has a flexural modulusbetween about 60,000 and about 80,000 psi (415 and 550 MPa). Goodresults have been obtained with the lithium ionomer resins havingflexural moduli in the range of about 60,000 psi to about 70,000 psi(415 to 485 MPa), e.g., SURLYN® 8118, SURLYN® 7930 and SURLYN® 7940.

[0142] Both the lithium and sodium ionomer resins preferably have about10 percent to about 90 percent of their carboxylic acid groupsneutralized by their respective metal ions. More preferably, both thelithium and sodium ionomer resins have their carboxylic acid groupsneutralized about 35 percent to about 65 percent by the metal ion.Preferably, the VLMI and harder ionomer resins include the samemonocarboxylic acid, e.g. either methacrylic or acrylic acid.

[0143] In order to adjust the characteristics of the cover stock, otherionomer resins besides sodium and lithium can be employed.

[0144] SURLYN® 8320, SURLYN® 8269 and SURLYN® 8265 have flexural moduliof 2,800 psi (20 MPa), 2,800 psi (20 MPa) and 7,100 psi (50 MPa),respectively. SURLYN® 8118, 7930 and 7940 have flexural moduli of 61,000psi (420 MPa), 67,000 psi (460 MPa) and 61,000 psi (420 MPa)respectively.

[0145] Conventionally, ionomer resins with different melt flow indexesare employed to obtain the desired characteristics of the cover stock.SURLYN® 8118, 7930 and 7940 have melt flow indices of about 1.4, 1.8,and 2.6 g/10 min., respectively. SURLYN® 8269 and SURLYN® 8265 both havea melt flow index of about 0.9 g/10 min. Preferably, the blend ofionomer resins used to make a cover of a golf ball in accordance withthe present invention has a melt flow index between about 1 to about 4g/10 min. and, more preferably, about 1 to about 3 g/10 min.

[0146] The combined amount of lithium ionomer resin and sodium ionomerresin used to make a cover in accordance with this embodiment of thepresent invention as described generally makes up at least about 90percent by weight of the total weight of the golf ball cover and,preferably, at least about 95 percent by weight. Additional materialswhich may be included in the golf ball cover are other SURLYN® resins;whitening agents such as titanium dioxide; dyes; UV absorbers; opticalbrighteners; and other additives which are conventionally included ingolf ball covers.

[0147] In another embodiment, the cover composition includes at leasttwo ionomer resins, preferably sodium ionomer resin and lithium ionomerresin, having similar flexural moduli. Preferably, the sodium ionomerresin is a copolymer including about 95 to about 80 parts by weight ofcopolymer of ethylene and about 12 to about 20 parts by weight of thecopolymer of acrylic or methacrylic acid in which about 10 percent toabout 90 percent of the acid groups are neutralized by sodium.

[0148] Preferably, the lithium ionomer resin is a copolymer includingabout 95 to about 80 parts by weight of ethylene and about 12 to about20 parts by weight of acrylic or methacrylic acid based on 100 parts byweight copolymer. Preferably, the lithium ionomer resin has about 10percent to about 90 percent of the acid groups neutralized by lithium.

[0149] Preferably, the sodium ionomer resin used in the presentinvention has a flexural modulus between about 60,000 and about 80,000psi (415 and 550 MPa).

[0150] The lithium ionomer resin used in the present invention has aflexural modulus between about 60,000 and about 80,000 psi (415 and 550MPa). Good results have been obtained with the sodium and lithiumionomer resins having flexural moduli in the range of about 60,000 psito about 70,000 psi (415 to 485 MPa).

[0151] Preferably, the ionomer resins incorporate the samemonocarboxylic acid, e.g., either methacrylic or acrylic acid.

[0152] Sodium ionomer resin sold by DuPont under the name SURLYN® 8920has worked well in the present invention. Good results have also beenobtained with a lithium ionomer resin sold under the trade name SURLYN®7940 by DuPont.

[0153] The cover layer employed in the present invention preferably havea Shore D hardness of about 60 to about 72, more preferably about 65 toabout 70 and most preferably about 68 to about 70.

[0154] Castable reactive liquid materials are particularly preferred forthe cover layers of the balls of the present invention. As used herein,the term “castable reactive liquid material” may refer to thermoset orthermoplastic materials. In a preferred embodiment, the castablereactive liquid material is a thermoset material.

[0155] In one embodiment, the castable reactive liquid material is casturethane or polyurethane. Polyurethane is a product of a reactionbetween a polyurethane prepolymer and a curing agent. The polyurethaneprepolymer is a product formed by a reaction between a polyol and adiisocyanate. Often a catalyst is employed to promote the reactionbetween the curing agent and the polyurethane prepolymer. In the case ofcast polyurethanes, the curing agent is typically either a diamine orglycol.

[0156] In another preferred embodiment, the castable reactive liquidmaterial is a thermoset cast polyurethane. Thermoset cast polyurethanesare generally prepared using a diisocyanate, such as 2,4-toluenediisocyanate (TDI), methylenebis-(4-cyclohexyl isocyanate) (HMDI), orpara-phenylene diisocyanate (“PPDI”) and a polyol which is cured with apolyamine, such as methylenedianiline (NDA), or a trifunctional glycol,such as trimethylol propane, or tetrafunctional glycol, such asN,N,N′,N′-tetrakis(2-hydroxpropyl)ethylenediamine. However, any suitablecast or non-cast thermoset polyurethane may be employed to form outercover layers of the present invention.

[0157] Other suitable thermoset materials contemplated for the coverlayers include, but are not limited to, thermoset urethane ionomers andthermoset urethane epoxies. Examples of suitable thennoset polyurethaneionomers are disclosed in U.S. Pat. Nos. 5,334,673 and 5,692,974, whichare incorporated in their entirety by reference herein. Other examplesof thermoset materials include polybutadiene, natural rubber,polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber,which are particularly suitable when used in an intermediate layer of agolf ball.

[0158] When the cover includes more than one layer, e.g., an inner coverlayer and an outer cover layer, various constructions and materials aresuitable. For example, as disclosed in U.S. Pat. Nos. 5,803,831 and6,210,293, which are incorporated in their entirety by reference herein,an inner cover layer may surround the intermediate layer with an outercover layer disposed thereon or an inner cover layer may surround aplurality of intermediate layers.

[0159] When using an inner and outer cover layer construction, the outercover layer material is preferably a thermoset material that includes atleast one of a castable reactive liquid material and reaction productsthereof, as described above, and preferably has a hardness from about 30Shore D to about 60 Shore D. In one embodiment, the outer cover layer isthin, preferably less than about 0.05 inches, and more preferably fromabout 0.02 inches to about 0.045 inches.

[0160] The inner cover layer may be formed from a wide variety of hard(about 65 Shore D or greater, preferably from about 69 Shore D to about74 Shore D), high flexural modulus resilient materials, which arecompatible with the other materials used in the adjacent layers of thegolf ball. The inner cover layer materials preferably has a flexuralmodulus of about 65,000 psi or greater. In one embodiment, the flexuralmodulus of the inner cover layer material is from about 70,000 psi toabout 120,000 psi.

[0161] Suitable inner cover layer materials include the hard, highflexural modulus ionomer resins and blends thereof as disclosed in U.S.Pat. No. 5,885,172, which is incorporated in its entirety by referenceherein. These ionomers are obtained by providing a cross metallic bondto polymers of monoolefin with at least one member selected from thegroup consisting of unsaturated mono- or di-carboxylic acids having 3 to12 carbon atoms and esters thereof (the polymer contains 1 to 50 percentby weight of the unsaturated mono- or di-carboxylic acid and/or esterthereof). More particularly, such acid-containing ethylene copolymerionomer component includes E/X/Y copolymers where E is ethylene, X is asoftening comonomer such as acrylate or methacrylate present in 0-50(preferably 0-25, most preferably 0-20), weight percent of the polymer,and Y is acrylic or methacrylic acid present in 5-35 (preferably atleast about 16, more preferably at least about 16-35, most preferably atleast about 16-20) weight percent of the polymer, wherein the acidmoiety is neutralized 1-90 percent (preferably at least 40 percent, mostpreferably at least about 60 percent) to form an ionomer by a cationsuch as lithium*, sodium*, potassium, magnesium*, calcium, barium, lead,tin, zinc* or aluminum (*=preferred), or a combination of such cations.Specific acid-containing ethylene copolymers include ethylene/acrylicacid, ethylene/methacrylic acid, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/iso-butyl acrylate, ethylene/acrylic acid/iso-butyl acrylate,ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylicacid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylicacid/methyl methacrylate, and ethylene/acrylic acid/n-butylmethacrylate. Preferred acid-containing ethylene copolymers includeethylene/methacrylic acid, ethylene/acrylic acid, ethylene/methacrylicacid/n-butyl acrylate, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/methyl acrylate and ethylene/acrylicacid/methyl acrylate copolymers. The most preferred acid-containingethylene copolymers are ethylene/methacrylic acid, ethylene/acrylicacid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

[0162] Examples of other suitable inner cover materials includethermoplastic or thermoset polyurethanes, polyetheresters,polyetheramides, or polyesters, dynamically vulcanized elastomers,functionalized styrene-butadiene elastomers, metallocene polymers,polyamides such as nylons, acrylonitrile butadiene-styrene copolymers(ABS), or blends thereof Suitable thermoplastic polyetheresters includematerials which are commercially available from DuPont under thetradename Hytrel®. Suitable thermoplastic polyetheramides includematerials which are available from Elf-Atochem under the tradenamePebax®.

[0163] The multi-layer golf ball of the invention can have an overalldiameter of any size. Although the United States Golf Associationspecifications limit the minimum size of a competition golf ball to1.680 inches in diameter or more, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

[0164] The golf balls of the present invention have an overall maximumcompression of about 85, preferably about 75 to about 85, morepreferably about 80 to about 85 and most preferably about 82.

[0165] Golf Ball Assembly

[0166] The center 11, as shown in FIG. 1, is preferably formed bycompression molding a sphere from a prep of center material. Compressionmolding solid centers is well known in the art.

[0167] In one embodiment, the golf ball of the present invention may beformed with a laminate process, as shown in FIGS. 2 and 3. In order toform multiple layers around the center according to this embodiment ofthe invention, a laminate 20 is first formed. The laminate 20 includesat least two layers and, preferably, three layers 22, 23, 24. In oneembodiment, the laminate is formed by mixing uncured core material to beused for each layer and calendar rolling the material into thin sheets32, 33, 34. In another embodiment, the laminate is formed by mixinguncured intermediate layer material and rolling the material into sheets32, 33, 34. The laminate sheets 32, 33, 34 are stacked together to formthe laminate 20 having three layers 22, 23, 24 using calender rollingmills. In another embodiment, however, the sheets 32, 33, 34 are made byextrusion.

[0168] In an alternate embodiment, the laminate 20 can be furtherconstructed using an adhesive between each layer of material.Preferably, an epoxy resin such as Epoxy Resin #1028 from RBC Industriesin Warwick, R.I. is used. The adhesive should have good shear andtensile strength and, preferably the adhesive should have a tensilestrength over about 1500 psi. Still further, the adhesive should notbecome brittle when cured. An adhesive having a Shore D hardness of lessthan 60 when cured is preferred. The adhesive layer applied to thesheets should be very thin and preferably, less than 0.004 inches thick.

[0169] Preferably, each laminate sheet is formed to a thickness that isslightly larger than the thickness of the layers 12, 13, 14 in thefinished golf ball 10. Each of these thicknesses can be varied, but allhave a thickness of preferably less than about 0.1 inches. Preferably,the sheets are formed to thicknesses that are less than 0.05 inches andthe laminate thickness is less than 0.15 inches. The sheets 32, 33 and34 should have very uniform thicknesses, i.e., the thickness of eachsheet should not vary more than about 0.005 inches.

[0170] The next step in the method, as shown in FIGS. 4-7, is to formmultiple layers around the center. This is preferably accomplished byplacing two laminates 20, 21 in between a top mold 36 and a bottom mold37, as illustrated in FIG. 4. The molds 36, 37 are formed of mold frames38 and replaceable mold halves 39 such as that described in U.S. Pat.No. 4,508,309 to Brown, the disclosure of which is incorporate in itsentirety by reference herein. The laminates 20, 21 are formed to thecavities in the mold halves 39.

[0171] In one embodiment, the laminates 20, 21 are cut into patternsthat, when joined, form a laminated layer around the center 11. Forexample, as illustrated in FIG. 5, the laminates 20, 21 may be cut intofigure 8-shaped or barbell-like patterns, similar to a baseball or atennis ball cover. Other patterns, such as curved triangles,hemispherical cups, ovals, or any like patterns that may be joinedtogether to form a laminated layer around the center 11 may also beused. The patterns may then be placed in between molds 36, 37 and formedto the cavities in the mold halves 39.

[0172] In one embodiment, the laminates are suction formed to thecavities by using a vacuum source 40. The vacuum source 40 suction formsthe laminates 20, 21 to the half mold cavities 39 so that uniformity inlayer thickness is maintained.

[0173] After the laminates 20, 21 have been formed to the cavities,centers 111 are then inserted between the laminates, as shown in FIG. 6.The laminates 20, 21 are then compression molded about the center 11under conditions of temperature and pressure that are well known in theart.

[0174] The half molds 39 have a plurality of vents 41, as shown in FIGS.7 and 8. The compression molding step includes flowing excess layermaterial from the laminates 20, 21 through at least three vents 41 sothat the flow of laminate material is symmetrical about the center 11and so that the center 11 does not shift due to lateral flow patterns.In a preferred embodiment, the half molds 39 have 4 to 6 vents.

[0175] The next step in the present invention is to form a cover 15around the golf ball core 16, i.e., the inner components of the golfball. The core 16, including center 11 and layers 12, 13, 14, issupported within a pair of cover mold-halves 50, 51 by a plurality ofretractable pins 52, as shown in FIG. 9. The retractable pins 52 areactuated by conventional means known to those of ordinary skill in theart of mold design.

[0176] After the mold-halves 50, 51 are closed together with the pins 52supporting the core 16, the cover material is injected into the mold ina liquid state through a plurality of injection ports or gates 49, asshown in FIG. 10. Gates 49 can be edge gates or sub-gates. With edgegates, the resultant golf balls are all interconnected and may beremoved from the mold-halves 50, 51 together in a large matrix.Sub-gating automatically separates the mold runner from the golf ballsduring the ejection of the golf balls from mold-halves 50, 51.

[0177] As illustrated in FIG. 11, retractable pins 52 are retractedafter a predetermined amount of cover material has been injected intothe mold-halves 50, 51. The predetermined amount of cover material issubstantially all of the material to be injected. Thus, the core 16 issubstantially surrounded by cover material and does not shift when theretractable pins 52 are removed. This allows the liquid cover materialto flow and substantially fill the cavity between the core 16 and themold-halves 50, 51. At the same time, concentricity is maintainedbetween the core 16 and the mold-halves 50, 51.

[0178] The cover material is allowed to solidify around the core 16,thereby forming cover 15. Golf ball 10 is then ejected from mold-halves50, 51, and finished using processes which are well known in the art.The temperatures and curing time for mold-halves 50, 51 are generallyknown in the art and are dependent on the material that is being usedfor cover 15.

[0179] In another embodiment, shown in FIG. 12, the cover 15 is formedusing cover layer hemispheres 55, 56. Two cover layer hemispheres 55, 56are preformed of the desired cover material, preferably, by an injectionmolding process. The hemispheres 55, 56 are positioned around the core16, thereby forming an assembly 57. Assembly 57 is placed into acompression mold 58 that includes two compression mold-halves 53, 54.Mold-halves 53, 54 are advanced toward each other until their matingsurfaces touch, and the mold 58 is heated to melt the hemispheres.Mold-halves 53, 54 compress and heat the hemispheres 55, 56 about thecore 16 to mold the cover material thereto.

[0180] While the embodiments above are directed to the use of laminatesto form the golf balls of the present invention, the construction of thegolf balls of the present invention are not limited to the embodimentsdescribed above and can be made by any conventional processes employedin the golf ball art. For example, the solid cores can be eitherinjection or compression molded. The intermediate layer may then besubsequently injection or compression molded about the core. It isimportant that the intermediate layer material be able to sustain thetemperatures applied during the application of the cover layer. Thecover layer or layers may then be injection or compression molded orcast about the intermediate layer.

[0181] Specific Golf Ball Constructions

[0182] Various embodiments of the golf balls are outlined below. Thegolf balls of the invention, however, variation of these embodiments arecovered as well. Properties such as hardness, Bayshore resilience,flexural modulus, center diameter, and layer thickness of the golf ballsof the present invention have been found to affect play characteristicssuch as spin, initial velocity and feel of golf balls.

[0183] In one embodiment, the center 11 and each of the layers 12, 13,14 are formed of a thermoset rubber, such as polybutadiene rubber. Inthis embodiment, a golf ball core 16 has a center 11 and three layers12, 13 and 14. The center diameter should be greater than about 1 inchand, preferably, should be about 1.25 to 1.45 inches. The most preferredcenter has a diameter of about 1.4 inches. Each of the layerssurrounding the center should have a thickness of less than about 0.1inches and preferably, less than about 0.05 inches. The most preferredthickness of the layers is about 0.03 to about 0.05 inches where thethickness of the third layer is equal to or less than the thickness ofthe first and second layers. Moreover, the center 11 of the golf ballpreferably has an outer diameter of greater than 60 percent of thefinished ball 10 diameter. Most preferably, the center 11 has a diameterthat is at least 75 percent of the diameter of the finished ball 10.

[0184] A small center of 1 inch or less and relatively thick corelayers, each having a thickness of greater than 0.1 inches, decreasesball initial velocity and reduces the ball spin rate effects. Whenimpacting a golf ball with different clubs within a set, the impactspeed and the impact angle are changed. On an average, for a tourprofessional the impact speed of a driver is about 110 miles an hour.The average professional 5 iron impact speed is around 90 miles an hourand the wedge impact velocity is less than about 80 miles an hour.Moreover, the force on the golf ball must be broken up into twocomponents, the normal force that is normal to the club face and thetangential force that is parallel to the club face. Since mostprofessionals use a driver having a loft of about 10 degrees, thetangential force is significantly less than the normal force. However,when using a wedge having a loft between 48 and 60 degrees, thetangential force becomes very significant. For example, experimentaldata shows that with a clubhead having an impact velocity of about 95miles an hour and an angle of 20 degrees, a two piece ball has a maximumdeflection of about 0.151 inches. When hit with a clubhead at 95 milesan hour and an impact angle of 40 degrees, the ball has a maximumdeflection of about 0.128 inches or a difference of 0.023 inches. Thus,the impact deflection depends significantly on the impact angle, and byhaving outer layers of less than 0.1 inches, the spin characteristics ofthe ball is altered for different clubs within a set as discussed inmore detail below.

[0185] For a high spin rate ball that also has good driver trajectorycharacteristics, the center 11 of the golf ball should have a Shore Chardness of about 70 or less. The first layer 12 should be harder thanthe center 11 and should have a Shore C hardness of about 70 to about75. The second layer 13 should be harder than the first layer 12 andhave a Shore C hardness of about 72 to about 77. The third layer orouter layer 14 should be harder than the second layer 13 and have aShore C hardness of about 75 to about 80. The cover 15 of the firstembodiment golf ball should be a soft cover and have a Shore D of lessthan 60. Moreover, the center 11, layers 12, 13 and 14 and the cover 15should be configured to provide a golf ball compression of less than 85and more preferably, less than about 80.

[0186] By creating a core 16 with relatively thin outer layers thatprogressively get harder, the spin rate of the ball is surprisingly goodfor a player that desires a high spin rate golf ball. More particularly,when this type of player hits the ball with a short iron, only the outerlayer and cover affect the spin rate of the ball. By incorporating avery hard core outer layer and a soft cover, the spin rate is maximizedfor the short iron shot such as a wedge having an angle of about 48 to60 degrees. In order to reduce the spin rate a little for middle ironshots such as a 6 iron having aloft of about 32 degrees to make surethat sufficient distance is obtained, the second layer is softer thanthe third layer. Similarly, to decrease the spin rate, provide gooddistance and a good trajectory for long irons such as a 3 iron having aloft of about 20 degrees, the first layer 1 is softer than the secondlayer 12. Finally, for a low spin rate with the driver having a loft ofabout 8 to 12 degrees, the center is made very soft.

[0187] Solid cores having diameters of about 1.58 inches may also bemade using the compositions of the core materials outline above. Coreshaving the centers as defined above preferably have a compression ofabout 50. The first layer composition preferably has a compression ofabout 75. Preferably, the first layer material will have a compressionthat is over 25 percent greater than the center material compression.The second layer composition preferably has a compression of about 85and, thus, has a greater compression than the first layer. The thirdlayer composition has a compression of about 110, which is significantlygreater than the second layer. Preferably, the third layer compressionis more than 75 percent greater than the center material compression.

[0188] In a preferred embodiment, the cover material includes a blend oftwo materials, a very soft material and a harder material. Preferably,the cover includes about 75 to about 25 parts by weight based on 100parts by weight resin (phr) of a low flexural modulus ionomer resin; andabout 25 to about 75 pph of a standard ionomer resin. The low flexuralmodulus ionomer is preferably a sodium ionomer resin and constitutesabout 40 pph to about 60 pph of the ionomer blend and the standardflexural ionomer is a lithium ionomer resin and constitutes about 60 pphto about 40 pph of the ionomer blend. The sodium ionomer resin ispreferably a copolymer including about 95 to about 80 parts by weight ofcopolymer of ethylene and about 5 to about 12 parts by weight of thecopolymer of acrylic or methacrylic acid in which about 10% to about 90%of the acid groups are neutralized by sodium. Preferably, lithiumionomer resin is a copolymer including about 95 to about 80 parts byweight of ethylene and about 10 to about 16 parts by weight of acrylicor methacrylic acid based on 100 party by weight copolymer. Preferably,the lithium ionomer resin has about 10 percent to about 90 percent ofthe acid groups neutralized by lithium.

[0189] Preferably, the low flexural modulus sodium ionomer resin used inthis embodiment has a flexural modulus between about 1,000 psi and about20,000 psi (5 MPa and 140 MPa) and, more preferably, between about 2,000psi and about 10,000 psi (10 MPa to 70 Mpa). The lithium ionomer resinpreferably has a high flexural modulus which is above about 60,000 psi(415 MPa). More preferably, the lithium ionomer resin used in thepresent invention has a flexural modulus between about 60,000 and about80,000 psi (415 and 550 MPa). Good results have been obtained with thelithium ionomer resins having flexural moduli in the range of about60,000 psi to about 70,000 psi (415 to 485 MPa).

[0190] In this embodiment, both the lithium and sodium ionomer resinspreferably have about 10 percent to about 90 percent of their carboxylicacid groups neutralized by their respective metal ions. More preferably,both the lithium and sodium ionomer resins have their carboxylic acidgroups neutralized about 35% to about 65% by the metal ion.

[0191] In addition, the ionomer resins preferably include the samemonocarboxylic acid, e.g. either methacrylic or acrylic acid.

[0192] In one embodiment, 55 weight percent SURLYN® 8320 and 45 weightpercent SURLYN® 7940 are included in the cover blend, wherein the blendhas a hardness of 55 Shore D. In another embodiment, 45 weight percentSURLYN® 8320 and 55 weight percent SURLYN® 7940 are included in thecover blend with a hardness of 59 Shore D.

[0193] In a second embodiment, the center 11 and each of the layers 12,13, 14 also include a thermoset rubber, such as polybutadiene.

[0194] In this second embodiment, the golf ball core also has a center11 and three layers 12, 13, 14. The center 11 should be greater than 1.0inch and, preferably, about 1.25 to 1.45 inches in diameter. The mostpreferred center has a diameter of about 1.4 inches. Each of the layersshould have a thickness of less than about 0.1 inches and preferably,less than about 0.05 inches. The most preferred thickness of each of thelayers is about 0.03 inches. Again, by having outer layers of less than0.1 inches, the spin characteristics of the ball can be altered fordifferent clubs within a set.

[0195] The center 11 of the second embodiment golf ball should have aShore C hardness of greater than about 75 for low swing speed players.The first layer should be softer than the center and have a Shore Chardness of about 75 to 72. The second layer should be softer than thefirst layer and have a Shore C hardness of about 73 to 70. The thirdlayer should be the softest and have a Shore C hardness of less thanabout 70. The cover of the second embodiment golf ball should have goodresilience and durability. Preferably, the cover of the secondembodiment is a harder cover and includes a blend of about 50/50 byweight of two standard or high acid ionomers. Standard ionomers haveabout 15 parts by weight of acrylic or methacrylic acid. High acidionomers have about 17 or more parts by weight of acrylic or methacrylicacid.

[0196] By creating a golf ball core 16 with relatively thin outer layersthat progressively get softer, the feel and distance is optimized for alow swing speed player. More particularly, when the low swing speedplayer hits the ball with a short iron, only the outer or third layerand cover are compressed. By utilizing a soft core and a harder cover,the feel of the ball is relatively soft when compared to distance ballshaving hard covers and hard cores. In order to increase the distance formiddle irons while still providing a relatively soft feel, the secondlayer is made harder than the third layer. Similarly, to provide greaterresiliency for long irons, the first layer 11 is harder than the secondlayer. Finally, for maximum resiliency with the driver, the center ismade harder than each of the layers. Since the center 11 is large, i.e.,between about 1.25 and 1.45 inches in diameter, the ball has a highcompression and initial velocity. However, since the third layer issoft, the ball provides a surprisingly better feel than hard core/hardcover balls.

[0197] Preferably, the cover material of this embodiment should providegood resiliency and durability. In one embodiment, the cover materialincludes of a blend of two ionomer resins having relatively the sameflexural moduli, e.g., sodium ionomer resin and lithium ionomer resin.

[0198] Preferably, the sodium ionomer resin is a copolymer includingabout 95 to about 80 parts by weight of copolymer of ethylene and about12 to about 20 parts by weight of the copolymer of acrylic ormethacrylic acid in which about 10 percent to about 90 percent of theacid groups are neutralized by sodium.

[0199] The lithium ionomer resin is preferably a copolymer includingabout 95 to about 80 parts by weight of ethylene and about 12 to about20 parts by weight of acrylic or methacrylic acid based on 100 parts byweight copolymer. Preferably, the lithium ionomer resin has about 10percent to about 90 percent of the acid groups neutralized by lithium.

[0200] Preferably, the sodium ionomer resin used according to thisembodiment preferably has a flexural modulus between about 60,000 andabout 80,000 psi (415 and 550 Mpa). The lithium ionomer resin usedaccording to this embodiment preferably has a flexural modulus betweenabout 60,000 and about 80,000 psi (415 and 550 MPa). Good results havebeen obtained with the sodium and lithium ionomer resins having flexuralmoduli in the range of about 60,000 psi to about 70,000 psi (415 to 485MPa).

[0201] Preferably, the ionomer resins incorporate the samemonocarboxylic acid, e.g., either methacrylic or acrylic acid.

[0202] Sodium ionomer resin sold by DuPont under the name SURLYN® 8920has worked well in the present invention. Good results have also beenobtained with a lithium ionomer resin sold under the trade name SURLYN®7940 by DuPont.

[0203] The golf ball of the present invention can have an overalldiameter of any size. Although the United States Golf Association (USGA)specifications limit the minimum size of a competition golf ball to morethan 1.680 inches in diameter, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

EXAMPLES Example 1

[0204] Table 1 sets forth an example of the core contents, i.e., centerand inner layers, according to one embodiment of the invention. Thefillers used in the compositions of these examples are regrind andbarium sulfate (BaSO4). Vulcup 40KE® and Varox 231XL® are free radicalinitiators, and are a-a bis (t-butylperoxy) diisopropylbenzene and1,1-di (t-butylperoxy) 3,3,5-trimethyl cyclohexane, respectively. TABLE1 Core Compositions (pph, based on 100 parts of polybutadiene) Layer No.Center 1 2 3 Polybutadiene 100 100 100 100 Polywate 325 26 23 18 13Vulcup 40KE ® 0.3 0.3 0.3 0.3 Varox 231XL ® 0.6 0.5 0.5 0.5 BaSO₄ 31 2625 25 Zinc Diacrylate 30 32 35 47 SR-350 2 2 2 6 Calcium Oxide 3 0 0 0Zinc Oxide 0 3 6 6

[0205] The center 11 set forth in Table 1, has a Shore C hardness ofabout 65 at the center point thereof and a Shore C hardness of about 68at the midpoint between the center and the outer edge. The first layer12 is harder than the center 11 and has a Shore C hardness of about 71.The second layer 13 is harder than the first layer 12 and has a Shore Chardness of about 73. The third layer or outer layer 14 is harder thanthe second layer 13 and had a Shore C hardness of about 77. The cover 15of the first embodiment golf ball is a soft cover and includes a blendof about 50/50 by weight of very low flexural modulus ionomer and astandard ionomer. The golf ball preferably has a compression of about60.

[0206] The center 11 of the core 16 was compression molded to a diameterof about 1.39 inches and each of the three layers, 12, 13 and 14 had athickness of about 0.03 inches. Solid cores having diameters of about1.58 inches were made using the compositions of the core materials ofTable 1.

[0207] Cores having the center composition of Table 1 have a compressionof about 50. The first layer composition has a compression of about 75.The first layer material has a compression that is over 25 percentgreater than the center material compression. The second layercomposition has a compression of about 85 and, thus, has a greatercompression than the first layer. The third layer composition has acompression of about 110, which is significantly greater than the secondlayer. The third layer compression is more than 75 percent greater thanthe center material compression.

[0208] All the ingredients except the peroxides were mixed in a ProcessLab Brabender mixer to about 180-200° F. The peroxides were added in thesecond stage to the initial mixture, and the resulting mixture wasremoved from the Brabender and blended on a lab mill to insurehomogeneity. After mixing, the mixture was then hand rolled using alaboratory mill and cut into pieces or “preps”. To make the centers 11,the preps were then compression molded at about 160° C. (320° F.) forabout 15 minutes. To fabricate the outer layers, the polybutadienerubber material was rolled into flat sheets and the sheets were stackedto form a laminate. The laminate was then compression molded around thecenters as described above. To form the finished golf balls, the coreswere ground and inserted into two cover hemispheres of lithium-sodiumblends of SURLYN®.

[0209] The cover blends used in this example is set forth in Table 2.TABLE 2 Cover Compositions (pph) Example No. 1 2 SURLYN 8320 55% 45%SURLYN 7940 45% 55% Blend Hardness (Shore D) 55    59   

Example 2

[0210] The center of the second embodiment, as set forth in Table 3, hasa Shore C hardness of about 77. The first layer is softer than thecenter and has a Shore C hardness of about 73. The second layer issofter than the first layer and has a Shore C hardness of about 71. Thethird layer is softer than the second layer and has a Shore C hardnessof about 68. The cover of the second embodiment golf ball is a hardercover than that used with the first embodiment and includes a blend ofabout 50/50 by weight of a standard sodium ionomer and a standardlithium ionomer. The cover, as described in Table 4, has a Shore Dhardness of about 65 to 70.

[0211] Table 3 sets forth the contents of the golf ball core in thesecond embodiment. The compositions used to prepare the golf ball coreof this embodiment are all in parts per hundred (pph), based on 100parts of polybutadiene.

[0212] In the second embodiment, the center 11 of the core 16 wascompression molded to a diameter of about 1.39 inches and each of thethree layers, 12, 13 and 14 had a thickness of about 0.03 inches. TABLE3 Inner Ball Compositions (pph, based on 100 parts of polybutadiene)Layer No. Center 1 2 3 Polybutadiene 100 100 100 100 Polywate 325 13 1823 26 Vulcup 40KE ® 0.3 0.3 0.3 0.3 Varox 231XL ® 0.5 0.5 0.5 0.6 BaSO425 25 26 31 Zinc Diacrylate 47 35 32 30 SR-350 6 2 2 2 Calcium Oxide 0 00 3 Zinc Oxide 6 6 3 0

[0213] To make the core centers 11, preps were made and compressionmolded. To fabricate the outer layers, the polybutadiene rubber materialwas rolled into flat sheets and stacked into a laminate. The laminatewas then compression molded around the centers as described above. Toform the finished golf balls, the cores were ground and inserted intotwo cover hemispheres of standard lithium-sodium blends of SURLYN®.

Example 3

[0214] Table 4 below provides batch compositions for intermediate layerblends for forming the novel multilayer golf balls of the presentinvention. However, it is to be understood that the examples are onlyfor illustrative purposes and in no manner is the present inventionlimited to the specific disclosures therein.

[0215] In particular, batch numbers 2-4 provide intermediate layerblends including NUCREL® 960, HYTREL® 3078, and ZnO used to form theintermediate layers of the golf balls of the present invention. Batchnumber 1 provides a control intermediate layer blend. TABLE 4Intermediate Layer Formulations Flexural Batch % NUCREL ® % HYTREL ® %Modulus Specific # 960 3078 ZnO (psi) Gravity 1 — 80 20 4210 1.27 2 1075 15 5560 1.21 3 20 70 10 7710 1.17 4 30 65  5 7250 1.14

Example 4

[0216] Multilayer golf balls were made having intermediate layers formedfrom the batch compositions set forth in Table 4. Several dozen golfballs were formed using each batch composition and subsequently testedfor compression, spin rate and initial velocity.

[0217] The cores of all of the multilayer balls were formed bycompression molding a blend of the batch formulation set forth in Table5 below. All of the cores had a diameter of 1.39 inches and weremeasured to have compressions ranging from about 45 to about 55 andspecific gravities of from about 1.134 to about 1.146.

[0218] The intermediate layer blends of Table 4 were subsequentlyinjection molded about the cores to form the intermediate layers of theballs having an outer diameter of about 1.51 inches. TABLE 5 CoreFormulation Material Parts Per Hundred Polybutadiene (Shell 1220) 76.0Rubber (Enichem Br40) 24.0 Pigment 0.10 Zinc Diacrylate 24.79 CalciumOxide 2.16 Regrind 6.47 Peroxide (VAROX ®) 0.43 Peroxide (EF-60) (DBDB)0.16 Filler 22.64

[0219] All of the multilayer balls had a cover composition formed byinjection molding a blend including 50 percent SURLYN® 7940 and 50percent SURLYN® 8140 about the intermediate layers and were subsequentlyfinished using conventional clear coating and buffing techniques. Thefinished golf balls had an outer diameter of about 1.68 inches.

[0220] These balls were tested for initial velocity, compression, coverhardness and COR, the results of such tests are set forth in Table IIIbelow.

[0221] The balls were also tested for spin rate using a True Temper TestMachine configured to strike the balls with a driver and an 8-Iron. Alsotested for comparison purposes were conventional two piece “distance”balls (Titleist® HP2 Distance and Pinnacle® Gold). The test data for allof these balls is set forth in Tables 6-8 below. TABLE 6 Com- Cover COR³Velocity¹ pression¹ Weight¹ Hardness² (at Ball (ft/s) (Ball) (oz) (ShoreD) 125 ft/s) Pinnacle ® 252.5 95 1.605 68 0.809 Gold⁴ Titleist ® 253.099 1.600 71 0.810 HP2 Distance⁴ Ball 1 251.9 81 1.610 71 0.814 Ball 2252.3 84 1.584 72 0.814 Ball 3 252.2 84 1.588 71 0.813 Ball 4 251.9 841.590 69 0.810

[0222] TABLE 7 Spin Rates For Driver Ball Type Launch Angle (°) Spin(rpm) Club Speed (ft/s) Pinnacle ® Gold 9.1 ± 0.3 3032 ± 135 158.6 ± 0.6Titleist ® 9.0 ± 0.3 2977 ± 60  158.6 ± 1.0 HP2 Distance Ball 1 9.1 ±0.5 2973 ± 195 158.4 ± 0.6 Ball 2 9.1 ± 0.5 3001 ± 66  158.9 ± 0.7 Ball3 9.1 ± 0.4 3006 ± 121 158.9 ± 0.8

[0223] TABLE 8 Spin Rate For 8-Iron Ball Type Launch Angle (°) Spin(rpm) Club Speed (ft/s) Pinnacle ® Gold 19.2 ± 0.4 8160 ± 218 116.4 ±0.1 Titleist ® 19.4 ± 0.5 8375 ± 171 116.3 ± 1.3 HP2 Distance Ball 119.2 ± 0.5 7970 ± 246 116.2 ± 0.7 Ball 3 19.3 ± 0.2 7972 ± 168 116.5 ±0.9 Ball 4 19.4 ± 0.3 7940 ± 171 117.0 ± 1.3

[0224] As shown by results reported in Tables 6-8, golf balls having anintermediate layer including NUCREL® 960, HYTREL® 3078, and ZnO have ahigh initial velocity and low spin rate. Moreover, the balls of thepresent invention have initial velocities approaching those ofconventional two-piece “distance” balls, but have a considerably lowercompression, which provides a much softer feel, more like a wound ball.Still further, these balls are easy to manufacture compared to theconventional wound ball. Thus, these balls provide the advantages of twopiece “distance” balls with low spin rates and high velocity, but alsoprovide a softer feel than such balls.

Example 5

[0225] Multilayer golf balls were made having intermediate layers formedfrom a blend including 20 percent NUCREL® 960, 57 percent HYTREL® 3078,and 23 percent ZnO.

[0226] This intermediate layer blend was injection molded about coresformed from the batch formulation set forth in Table 5. A cover wasformed by injection molding a blend of 50 percent SURLYN® 7940, 47percent SURLYN® 8940, and 3 percent SURLYN® 8660 around the intermediatelayer and subsequently finishing the balls using conventional clearcoating and buffing techniques.

[0227] The balls were tested for initial velocity, compression, coverhardness and COR, as well as for spin rate when struck by a driver andan 8-Iron using a True Temper Test Machine. The results of such testsare set forth below in Tables 9-11 below. TABLE 9 Cover Velocity¹Compression¹ Weight¹ Hardness² COR³ Specific (ft/s) (Ball) (oz) (ShoreD) (at 125 ft/s) Gravity 251.5 82 1.607 69 0.801 1.27

[0228] TABLE 10 Club Launch Angle (°) Spin (rpm) Club Speed (ft/s)Driver  9.2 ± 0.5 3015 ± 221 160.3 ± 0.7 8 Iron 19.3 ± 0.6 7807 ± 252115.6 ± 0.8

[0229] TABLE 11 Mantle Layer Compositions and Properties Flex Tensile %Strain Hardness Resilience Modulus Modulus at Sample (Shore D) (%) (psi)(psi) Break 1A   0% Estane 58091 28 54  1,720   756 563  100% Estane58861 1B   25% Estane 58091 34 41  2,610  2,438 626   75% Estane 588611C   50% Estane 58091 44 31 10,360 10,824 339   50% Estane 58861 1D  75% Estane 58091 61 34 43,030 69,918 149   25% Estane 58861 1E  100%Estane 58091 78 46 147,240  211,288   10   0% Estane 58861 2A   0%Hytrel 5556 40 47  8,500  7,071 527  100% Hytrel 4078 2B   25% Hytrel5556 43 51 10,020  9,726 441   75% Hytrel 4078 2C   50% Hytrel 5556 4547 12,280 10,741 399   50% Hytrel 4078 2D   75% Hytrel 5556 48 53 13,68013,164 374   25% Hytrel 4078 2E  100% Hytrel 5556 48 52 12,110 15,231347   0% Hytrel 4078 3A   0% Hytrel 5556 30 62  3,240  2,078 810  100%Hytrel 3078 No Break 3B   25% Hytrel 5556 37 59  8,170  5,122 685   75%Hytrel 3078 3C   50% Hytrel 5556 44 55 15,320 10,879 590   50% Hytrel3078 3D   75% Hytrel 5556 53 50 19,870 16,612 580   25% Hytrel 3078 3E 100% Hytrel 5556 58 50 24,840 17,531 575   0% Hytrel 3078 4A   0%Hytrel 4078 46 51 11,150  8,061 597  100% Pebax 4033 4B   25% Hytrel4078 46 53 10,630  7,769 644   75% Pebax 4033 4C   50% Hytrel 4078 45 52 9,780  8,117 564   50% Pebax 4033 4D   75% Hytrel 4078 42 53  9,310 7,996 660   25% Pebax 4033 4E  100% Hytrel 4078 40 51  9,250  6,383 531  0% Pebax 4033 5A   0% Hytrel 3078 77 50 156,070  182,869   9  100%Estane 58091 5B   25% Hytrel 3078 65 48 87,680 96,543  33   75% Estane58091 5C   50% Hytrel 3078 52 49 53,940 48,941 102   50% Estane 58091 5D  75% Hytrel 3078 35 54 12,040  6,071 852   25% Estane 58091 5E  100%Hytrel 3078 29 50  3,240  2,078 810   0% Estane 58091 No Break 6A  100%Kraton 1921 29 59 24,300 29,331 515   0% Estane 58091   0% Surlyn 79406B   50% Kraton 1921 57 49 56,580 — 145   50% Estane 58091   0% Surlyn7940 6C   50% Kraton 1921 56 55 28,290 28,760 295   0% Estane 58091  50% Surlyn 7940 7A 33.3% Pebax 4033 48 50 41,240 30,032 294 33.3%Estane 58091 33.3% Hytrel 3078 7B   30% Pebax 4033 48 50 30,650 14,220566   40% Estane 58091   10% Hytrel 3078 7C   20% Pebax 4033 41 5424,020 16,630 512   40% Estane 58091   40% Hytrel 3078

[0230] While it is apparent that the illustrative embodiments of theinvention herein disclosed fulfill the objectives stated above, it willbe appreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. For instance, the thermoformingprocesses described herein may be used to form any portion of the ball.Likewise, the thermoformed shells may be placed around golf ball coresand any other golf ball component. Therefore, it will be understood thatthe appended claims are intended to cover all such modifications andembodiments which come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A method of making a golf ball comprising thesteps of: forming a core; thermoforming a plurality of shells;positioning two of said plurality of shells to form a layer around thecore; and forming a cover.
 2. The method of claim 1, wherein theplurality of shells are formed from laminated roll stock material. 3.The method of claim 2, wherein the roll stock comprises a firstlamination layer and a second lamination layer, wherein the firstlamination layer has a hardness greater than the second lamination layerby about 10 shore D or more.
 4. The method of claim 1, wherein theplurality of shells are vacuum formed.
 5. The method of claim 1 whereinthe step of thermoforming a plurality of shells comprises forming asheet of shells from roll stock.
 6. The method of claim 5, furthercomprising the step of cutting a first shell out of said sheet ofshells, wherein said first shell has a lip formed around its edge. 7.The method of claim 6, wherein said lip extends in a radial directionfrom the edge of the shell from about 0.05 inches to about 0.5 inches.8. The method of claim 7, wherein said lip is approximately circular inshape.
 9. The method of claim 8, further comprising the step of joiningsaid first shell with a second shell of similar construction anddimensions as the first shell.
 10. The method of claim 2, wherein eachlamination layer of the roll stock has a thickness of about 0.1 inchesor less.
 11. The method of claim 10, wherein each lamination layer ofthe roll stock has a thickness of about 0.05 inches or less.
 12. Themethod of claim 2, wherein at least one lamination layer of the rollstock comprises a thermoset material.
 13. The method of claim 12,wherein the thermoset material is polybutadiene.
 14. The method of claim2, wherein at least one lamination layer of the roll stock comprises athermoplastic material having a flexural modulus of about 10,000 psi orless.
 15. The method of claim 2, wherein at least one lamination layerof the roll stock comprises an ionomer resin.
 16. The method of claim 1,further comprising the step of compression molding the plurality ofshells around the core.
 17. The method of claim 1, wherein the formedcover has a thickness of about 0.05 inches or less.
 18. The method ofclaim 1, wherein the golf ball has a compression of about 85 or less.19. The method of claim 1, wherein the step of forming a cover comprisesinjection molding the cover around the golf ball.
 20. The method ofclaim 1, wherein the step of forming a cover comprises compressionmolding the cover around the golf ball.
 21. The method of claim 1,wherein the step of forming a cover comprises casting the cover aroundthe golf ball.
 22. The method of claim 2, wherein the roll stockcomprises a first lamination layer and a second lamination layer;wherein the first lamination layer is disposed proximal to the core andthe second lamination layer is disposed proximal to the cover; andwherein the core has a first hardness, the first lamination layer has asecond hardness greater than the first hardness, and the secondlamination layer has a third hardness greater than the second hardness.23. The method of claim 22, wherein the plurality of layers furthercomprises a third laminate layer having a fourth hardness, disposedbetween the first and second laminate layers, and wherein the fourthhardness is greater than the second hardness.
 24. The method of claim 2,wherein the roll stock comprises a first lamination layer and a secondlamination layer; wherein the first lamination layer is disposedproximal to the core and the second lamination layer is disposedproximal to the cover; and wherein the core has a first hardness, thefirst lamination layer has a second hardness less than the firsthardness, and the second lamination layer has a third hardness less thanthe second hardness.
 25. The method of claim 24, wherein the pluralityof layers further comprises a third laminate layer having a fourthhardness, disposed between the first and second laminate layers, andwherein the fourth hardness is less than the second hardness.
 26. A golfball comprising: a core; a plurality of thermoformed laminate layers;and a cover.
 27. The golf ball of claim 26, wherein the plurality ofthermoformed laminate layers comprises: a first laminate layercomprising at least one thermoplastic material, and a second laminatelayer comprising at least one thermoset material.
 26. The golf ball ofclaim 27, wherein the first layer is proximal to the core and the atleast one thermoplastic material comprises dynamically vulcanizedthermoplastic elastomers, functionalized styrene-butadiene elastomers,thermoplastic rubbers, thermoplastic urethanes, metallocene polymers,ionomer resins, or blends thereof.